US20070256301A1 - Method of manufacturing inkjet printhead using crosslinked polymer - Google Patents
Method of manufacturing inkjet printhead using crosslinked polymer Download PDFInfo
- Publication number
- US20070256301A1 US20070256301A1 US11/772,541 US77254107A US2007256301A1 US 20070256301 A1 US20070256301 A1 US 20070256301A1 US 77254107 A US77254107 A US 77254107A US 2007256301 A1 US2007256301 A1 US 2007256301A1
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- US
- United States
- Prior art keywords
- layer
- sacrificial layer
- substrate
- passage forming
- negative photoresist
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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- 229920006037 cross link polymer Polymers 0.000 title description 45
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- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 claims abstract description 61
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- 125000002723 alicyclic group Chemical group 0.000 claims abstract description 30
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- KUBDPQJOLOUJRM-UHFFFAOYSA-N 2-(chloromethyl)oxirane;4-[2-(4-hydroxyphenyl)propan-2-yl]phenol Chemical compound ClCC1CO1.C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 KUBDPQJOLOUJRM-UHFFFAOYSA-N 0.000 description 4
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1601—Production of bubble jet print heads
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1601—Production of bubble jet print heads
- B41J2/1603—Production of bubble jet print heads of the front shooter type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1631—Manufacturing processes photolithography
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1637—Manufacturing processes molding
- B41J2/1639—Manufacturing processes molding sacrificial molding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/164—Manufacturing processes thin film formation
- B41J2/1642—Manufacturing processes thin film formation thin film formation by CVD [chemical vapor deposition]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/164—Manufacturing processes thin film formation
- B41J2/1645—Manufacturing processes thin film formation thin film formation by spincoating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/164—Manufacturing processes thin film formation
- B41J2/1646—Manufacturing processes thin film formation thin film formation by sputtering
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49401—Fluid pattern dispersing device making, e.g., ink jet
Definitions
- the present general inventive concept relates to a method of manufacturing an inkjet printhead, and more particularly, to a method of manufacturing an inkjet resist composition printhead by photolithography using a crosslinked polymer.
- inkjet printheads are devices for printing a predetermined color image by ejecting small droplets of printing ink at a desired position on a recording sheet.
- Ink ejection mechanisms of an inkjet printer are generally categorized into two different types: a thermally driven type (bubble-jet type), in which a heat source is employed to form bubbles in ink thereby causing an ink droplet to be ejected, and an piezoelectrically driven type, in which an ink droplet is ejected by a change in ink volume due to deformation of a piezoelectric element.
- the inkjet printhead includes a substrate 10 , a passage forming layer 20 stacked on the substrate 10 , and a nozzle plate 30 formed on the passage plate 20 .
- An ink supply hole 51 is formed in the substrate 10 .
- the passage forming layer 20 has an ink chamber 53 to store ink and a restrictor 52 connecting the ink supply hole 51 and the ink chamber 53 .
- the nozzle layer 30 has a nozzle 54 through which the ink is ejected from the ink chamber 53 .
- the substrate 10 has a heater 41 for heating ink in the ink chamber 53 and an electrode 42 for supplying current to the heater 41 .
- Ink is supplied from an ink reservoir (not illustrated) to the ink chamber 53 through the ink supply hole 51 and the restrictor 52 .
- the ink filling the ink chamber 53 is heated by a heater 41 consisting of resistive heating elements.
- the ink boils to form bubbles and the bubbles expand so that the ink in the ink chamber 53 is ejected by a bubble pressure. Accordingly, the ink in the ink chamber 53 is ejected outside the ink chamber 53 through the nozzle 54 in the form of ink droplets.
- the conventional thermally-driven inkjet printhead having the above-described configuration can be monolithically manufactured by photolithography, and the photolithography manufacturing process thereof is illustrated in FIGS. 2A through 2E .
- a substrate 10 having a predetermined thickness is prepared, and a heater 41 for heating ink and an electrode 42 for supplying a current to the heater 41 are formed on the substrate 10 .
- a negative type photoresist composition is applied to the entire surface of the substrate 10 to a predetermined thickness and the negative type photoresist composition is then patterned in such a shape as to surround an ink chamber 53 (see FIG. 2E ) and a restrictor 52 (see FIG. 2E ) by photolithography, thereby forming a passage forming layer 20 .
- a space surrounded by the passage forming layer 20 is filled with a positive-type photoresist composition, thereby forming a sacrificial layer S.
- the positive-type photoresist composition is applied to the entire surface of the substrate 10 to a predetermined thickness and the positive-type photoresist composition is then patterned, thereby forming a sacrificial layer S.
- the positive-type photoresist composition is generally applied by spin coating, and the top surface of the applied positive-type photoresist is not planarized (i.e., has an uneven surface, as illustrated in FIGS. 2C and 2D ) due to the centrifugal force of the spin coating.
- the positive-type photoresist bulges upward around the passage forming layer 20 due to the centrifugal force provided during spin coating, as indicated by the double-dashed line illustrated in FIG. 2C . If the uneven surface of the positive-type photoresist is patterned, the sacrificial layer S protrudes upward at its peripheral edges, as illustrated in FIG. 2D .
- a negative type photoresist composition is applied to the passage forming layer 20 and the sacrificial layer S to a predetermined thickness and the negative type photoresist composition is then patterned by photolithography, thereby forming a nozzle layer 30 having a nozzle 54 .
- the bottom surface of the substrate 10 is wet-etched to form an ink supply hole 51 , and the sacrificial layer S is removed through the ink supply hole 51 , thereby forming the restrictor 52 and the ink chamber 53 in the passage forming layer 20 .
- a projecting edge of the sacrificial layer S made of the positive-type photoresist may react with a solvent contained in the crosslinked polymer resist composition, causing deformation or melting.
- a cavity C is formed between the passage forming layer 20 and the nozzle layer 30 .
- the passage forming layer 20 and the nozzle layer 30 are not suitably adhered to each other due to existence of the cavity C formed between the passage forming layer 20 and the nozzle layer 30 .
- the crosslinked polymer resist composition applied to the sacrificial layer S is patterned by exposure, development, and baking.
- broadband UV light including I-line (353 nm), H-line (405 nm), and G-line (436 nm)
- I-line 353 nm
- H-line 405 nm
- G-line 436 nm
- the H-line and the G-line each having a relatively long wavelength and a long penetration depth, affect both the crosslinked polymer resist composition forming the nozzle layer 30 and the positive photoresist forming the sacrificial layer S disposed under the nozzle layer 30 .
- a photosensitizer contained therein may be decomposed by the light, producing nitrogen (N 2 ) gas.
- the produced nitrogen gas expands during baking to lift the nozzle layer 30 , resulting in deformation of the nozzle layer 30 .
- the present general inventive concept provides a method of manufacturing an inkjet printhead that can easily control a shape and dimension of an ink passage by planarizing a top surface of a sacrificial layer, thereby improving uniformity of the ink passage, and an inkjet printhead manufactured by the method.
- the present general inventive concept provides an inkjet printhead having a planarized surface of a sacrificial layer to control a shape and a dimension of an ink passage, thereby improving uniformity of the ink passage and preventing deformation of a nozzle layer due to gas generated in the sacrificial layer.
- a method of manufacturing an inkjet printhead including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; applying a negative photoresist composition to the substrate having thereon the heater and the electrode and patterning the negative photoresist composition to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying the negative photoresist composition to the passage forming layer and the sacrificial layer and patterning the negative photoresist composition to form a nozzle layer having a nozzle; etching a rear surface of the substrate to form an ink supply hole; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a
- the monomers in the prepolymer can all have an identical formula.
- the monomers in the prepolymer can all have different formulas.
- the monomers in the prepolymer can include a mixture of some of the monomers having an identical formula and others of the monomers having different formulas.
- a method of manufacturing an inkjet printhead including: applying a first negative photoresist composition to a substrate having thereon a heater and an electrode; patterning the first negative photoresist composition to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying a second negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the passage forming layer and the sacrificial layer; patterning the second negative photoresist
- a method of manufacturing an inkjet printhead including: applying to a substrate a negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone; exposing the negative photoresist composition applied to the substrate to ultraviolet light to form a first crosslinked polymer; developing the first crosslinked polymer; applying a positive photoresist composition to the substrate and the first crosslinked polymer; exposing the positive photoresist composition applied to the substrate and the first crosslinked polymer to ultraviolet light to form a first sacrificial layer; developing the first sacrificial layer; applying the positive photoresist composition to the substrate, the first crosslinked polymer, and the
- the exposing of the negative photoresist composition applied to the substrate may include exposing the negative photoresist composition through a first photomask having a passage forming layer pattern to ultraviolet light to form the first crosslinked polymer.
- the exposing of the positive photoresist composition applied to the substrate and the first crosslinked polymer may include exposing the positive photoresist composition through a second photomask having an ink chamber pattern to ultraviolet light to form the first sacrificial layer.
- the exposing of the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first sacrificial layer may include exposing the positive photoresist composition through a second photomask having an ink chamber pattern to ultraviolet light to form the second sacrificial layer having a planarized upper surface.
- the method may further include repeatedly blank exposing the second sacrificial layer having the planarized upper surface until a height of the second sacrificial layer is substantially equal to a height of the passage forming layer, developing the blank exposed second sacrificial layer, applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the substrate and the second sacrificial layer, exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to ultraviolet light to form a second crosslinked polymer, and developing the second crosslinked polymer.
- the exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer may include exposing the negative photoresist composition through a third photomask having a nozzle layer pattern to ultraviolet light to form the second crosslinked polymer.
- the method may further include applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic backbone to the substrate and the second sacrificial layer, exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to ultraviolet light to form a second crosslinked polymer, and developing the second crosslinked polymer, in which the positive photoresist composition is an imide-based positive photoresist composition.
- a photolithography method including applying a first negative photoresist composition to a substrate having a heater and an electrode formed thereon, patterning the negative photoresist composition to form a passage forming layer, applying a positive photoresist composition to a location on the substrate surrounded by the passage forming layer, patterning the positive photoresist composition to form a sacrificial layer, applying a second negative photoresist composition including a prepolymer that a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the passage forming layer and the sacrificial layer, patterning the second negative photoresist composition to form a nozzle having a nozzle layer, and removing the sacrificial layer
- the first negative photoresist composition may include a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- the positive photoresist composition can be an imide-based positive photoresist composition.
- an inkjet printhead including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a nozzle layer, disposed on the passage forming layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- a height of the ink chamber can be substantially equal to a height of the passage forming layer.
- a height of the ink chamber can be greater than a height of the passage forming layer.
- the passage forming layer can include a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- an inkjet printhead intermediate useable to make an inkjet printhead including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; and a first crosslinked polymer resist layer, disposed on the substrate, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenol novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a sacrificial layer having a planarized upper surface disposed on a portion of the substrate substantially surrounded by the passage forming layer.
- the passage forming layer can include a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- the sacrificial layer can include an imide-based positive photoresist composition.
- a height of the sacrificial layer can be substantially equal to a height of the passage forming layer.
- a height of the sacrificial layer can be greater than a height of the passage forming layer.
- the inkjet printhead intermediate can further include a polymer layer, disposed on the sacrificial layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- a polymer layer disposed on the sacrificial layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- an inkjet printhead including: a substrate having a passage, at least one heater formed on a first portion of the substrate, at least one electrode formed on a second portion of the substrate, a passage forming layer formed on a third portion of the substrate, and a nozzle layer formed on the passage forming layer, having a planarized surface facing the substrate.
- the surface of the nozzle layer and a surface of the passage forming layer can form an angle without a cavity on at least one of the surfaces of the nozzle layer and the passage forming layer.
- an inkjet printhead including forming a substrate having a passage, forming at least one heater on a first portion of the substrate, forming at least one electrode on a second portion of the substrate, forming a passage forming layer on a third portion of the substrate, and forming a nozzle layer having a planarized surface facing the substrate on the passage forming layer.
- the forming of the nozzle layer having the planarized surface facing the substrate on the passage forming layer can include forming an angle without a cavity between the surface of the nozzle layer and a surface of the passage forming layer.
- an inkjet printhead including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; coating a negative photoresist composition on the substrate having thereon the heater and the electrode and patterning the negative photoresist composition using a photolithography process to form a passage forming layer that defines an ink passage; forming a sacrificial layer on the substrate having thereon the passage forming layer so as to cover the passage forming layer; planarizing upper surfaces of the passage forming layer and the sacrificial layer using a polishing process; coating a negative photoresist composition on the passage forming layer and the sacrificial layer and patterning the negative photoresist composition using a photolithography process to form a nozzle layer having a nozzle; forming an ink feed hole in the substrate; and removing the sacrificial layer, wherein the negative photoresist composition
- the polishing process may be a chemical mechanical polishing (CMP) process.
- the substrate may be a silicon wafer.
- an upper surface of a sacrificial layer can be planarized, and thus, it is possible to easily control the shape and dimension of an ink passage, thereby improving uniformity of the ink passage. Moreover, no gas is generated in the sacrificial layer, thereby avoiding deformation of a nozzle layer.
- FIG. 1 is a schematic perspective view illustrating a structure of a conventional thermally-driven inkjet printhead
- FIGS. 2A through 2E are cross-sectional views illustrating a method of manufacturing the conventional inkjet printhead illustrated in FIG. 1 ;
- FIGS. 3A through 3R are cross-sectional views illustrating a method of manufacturing an inkjet printhead according to an embodiment of the present general inventive concept
- FIGS. 4A through 4F are cross-sectional views illustrating a method of manufacturing inkjet printhead according to an embodiment of the present general inventive concept.
- FIG. 5A is a vertical cross-sectional view of an inkjet printhead according to an embodiment of the present general inventive concept
- FIG. 5B is an enlarged view illustrating the vertical cross-sectional view in FIG. 5A ;
- FIGS. 6A through 6L are sectional views illustrating a method of manufacturing an inkjet printhead according to an embodiment of the present invention.
- FIGS. 7A and 7B are images showing a passage forming layer and a sacrificial layer after a chemical mechanical polishing (CMP) process in a method of manufacturing an inkjet printhead according to an embodiment of the present invention.
- CMP chemical mechanical polishing
- FIGS. 8A and 8B are vertical sectional views illustrating an inkjet printhead manufactured by a method of manufacturing an inkjet printhead according to an embodiment of the present invention.
- the present general inventive concept provides a method of manufacturing an inkjet printhead, the method including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; applying a negative photoresist composition to the substrate having thereon the heater and the electrode and patterning the negative photoresist composition to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying the negative photoresist composition to the passage forming layer and the sacrificial layer and patterning the negative photoresist composition to form a nozzle layer having a nozzle; etching a rear surface of the substrate to form an ink supply hole; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a glycidyl ether functional group or a ring-
- the negative photoresist composition may include the prepolymer, a cationic photoinitiator, and a solvent.
- the prepolymer of the negative photoresist composition may form a crosslinked polymer by exposing the prepolymer to an actinic radiation.
- the prepolymer may be prepared from a backbone monomer unit selected from the group consisting of phenol, o-cresol, p-cresol, bisphenol-A, an alicyclic compound, and mixtures thereof.
- the prepolymer may include at least one represented by Formulas 1-7 below:
- m is an integer ranging from 1 to 20
- n is an integer ranging from 1 to 20.
- the prepolymer may also be addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)-1-butanol (which are commercially available under the trade name of EHPH-3150).
- the cationic photoinitiator can be, for example, a sulfonium salt or an iodonium salt.
- the solvent may be at least one compound selected from the group consisting of -butyrolactone, propylene glycol methyl ether acetate (PGMEA), tetrahydrofuran (THF), methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and mixtures thereof.
- PGMEA propylene glycol methyl ether acetate
- THF tetrahydrofuran
- methyl ethyl ketone methyl isobutyl ketone
- cyclopentanone cyclopentanone
- an inkjet printhead can be manufactured by a method including applying a first crosslinked polymer resist composition to a substrate having a heater and an electrode and patterning the first crosslinked polymer resist composition to form a passage forming layer that surrounds an ink passage, patterning the substrate having the passage forming layer by photolithography at least twice, forming a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer, applying a second crosslinked polymer resist composition to the passage forming layer and the sacrificial layer and patterning the second crosslinked polymer resist composition to form a nozzle layer having a nozzle, and removing the sacrificial layer.
- a step difference between a chamber layer of the inkjet printhead and the sacrificial layer is not greater than about 3 ⁇ m.
- Monomers forming the prepolymer can all have an identical formula.
- the monomers forming the prepolymer can all have different formulas.
- the monomers forming the prepolymer can include a mixture of some of monomers having an identical formula and others of monomers having different formulae.
- the present general inventive concept also provides a method of manufacturing an inkjet printhead, the method including: applying to a substrate a negative photoresist composition including a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone; exposing the negative photoresist composition applied to the substrate to ultraviolet (UV) light to form a first crosslinked polymer; developing the first crosslinked polymer; applying a positive photoresist composition to the substrate and the first crosslinked polymer; exposing the positive photoresist composition applied to the substrate and the first crosslinked polymer to UV light to form a first sacrificial layer; developing the first sacrificial layer; applying the positive photoresist composition to the substrate, the first crosslinked polymer, the first sacrificial layer; exposing the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first
- the exposing of the negative photoresist composition applied to the substrate may include exposing the negative photoresist composition to UV light using a first photomask having a passage forming layer pattern to form the first crosslinked polymer.
- the exposing of the positive photoresist composition applied to the substrate and the first crosslinked polymer may include exposing the positive photoresist composition to UV light using a second photomask having an ink chamber pattern to form the first sacrificial layer.
- the exposing of the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first sacrificial layer may include exposing the positive photoresist composition to UV light using a second photomask having an ink chamber pattern to form the second sacrificial layer having a planarized upper surface.
- the method may further include repeatedly blank exposing the second sacrificial layer having the planarized upper surface until a height of the second sacrificial layer is substantially equal to a height of the passage forming layer; developing the blank exposed second sacrificial layer; applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the substrate and the second sacrificial layer; exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to UV light to form a second crosslinked polymer; and developing the second crosslinked polymer.
- the exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer may include exposing the negative photoresist composition to UV light using a third photomask having a nozzle layer pattern to form the second crosslinked polymer.
- the method may further include applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the substrate and the second sacrificial layer; exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to UV light to form a second crosslinked polymer; and developing the second crosslinked polymer, wherein the positive photoresist composition is an imide-based positive photoresist composition.
- the exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer can include exposing the negative photoresist composition to UV light using a third photomask having a nozzle layer pattern to form the second crosslinked polymer.
- the present general inventive concept also provides an inkjet printhead including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a nozzle layer, disposed on the passage forming layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- a height of the ink chamber can be substantially equal to a height of the passage forming layer.
- a height of the ink chamber can be greater than a height of the passage forming layer.
- the passage forming layer can include a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- the present general inventive concept also provides an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; and a first polymer layer, disposed on the substrate, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- the present general inventive concept also provides an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a sacrificial layer having a planarized upper surface disposed on a portion of the substrate substantially surrounded by the passage forming layer.
- the passage forming layer may include a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- the sacrificial layer may include an imide-based positive photoresist composition.
- a height of the sacrificial layer may be substantially equal to a height of the passage forming layer.
- a height of the sacrificial layer may be greater than a height of the passage forming layer.
- the inkjet printhead intermediate may further include a polymer layer, disposed on the sacrificial layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- a polymer layer disposed on the sacrificial layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- the present general inventive concept also provides a method of manufacturing an inkjet printhead, the method including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; coating a negative photoresist composition on the substrate having thereon the heater and the electrode and patterning the negative photoresist composition using a photolithography process to form a passage forming layer that defines an ink passage; forming a sacrificial layer on the substrate having thereon the passage forming layer so as to cover the passage forming layer; planarizing upper surfaces of the passage forming layer and the sacrificial layer using a polishing process; coating the negative photoresist composition on the passage forming layer and the sacrificial layer and patterning the negative photoresist composition using a photolithography process to form a nozzle layer having a nozzle; forming an ink feed hole in the substrate; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a g
- the polishing process may be a chemical mechanical polishing (CMP) process.
- the substrate may be a silicon wafer.
- the formation of the passage forming layer may include forming a first photoresist layer by coating the negative photoresist composition on the entire surface of the substrate; exposing the first photoresist layer using a first photomask having an ink passage pattern; and forming the passage forming layer by developing the first photoresist layer to remove an unexposed portion of the first photoresist layer.
- the sacrificial layer may include a positive photoresist or a non-photosensitive soluble polymer.
- the positive photoresist may be an imide-based positive photoresist.
- the non-photosensitive soluble polymer may be at least one selected from the group consisting of a phenolic resin, a polyurethane resin, an epoxy resin, a polyimide resin, an acrylic resin, a polyamide resin, an urea resin, a melamine resin, and a silicone resin.
- the term “soluble” refers to characteristics that can be dissolved in a solvent.
- the sacrificial layer may be formed to be higher than the passage forming layer.
- the sacrificial layer may be formed using a spin coating process.
- the upper surfaces of the passage forming layer and the sacrificial layer may be polished using a polishing process such as a chemical mechanical polishing process to reach a desired height of the ink passage.
- the formation of the nozzle layer may include forming a second photoresist layer by coating the negative photoresist composition on the passage forming layer and the sacrificial layer; exposing the second photoresist layer using a second photomask having a nozzle pattern; and forming the nozzle layer having the nozzle by developing the second photoresist layer to remove an unexposed portion of the second photoresist layer.
- the formation of the ink feed hole may include coating a photoresist on a rear surface of the substrate; forming an etch mask for forming the ink feed hole by patterning the photoresist; and etching a rear surface portion of the substrate exposed through the etch mask to form the ink feed hole.
- the rear surface of the substrate may be etched by a dry etching process using plasma or a wet etching process using tetramethylammonium hydroxide (TMAH) or KOH as an etchant.
- TMAH tetramethylammonium hydroxide
- the negative photoresist composition may further include a cationic photoinitiator and a solvent, in addition to the prepolymer having the glycidyl ether functional group.
- the prepolymer having the glycidyl ether functional group may be prepared from a backbone monomer unit selected from the group consisting of phenol, o-cresol, p-cresol, bisphenol-A, an alicyclic-based compound, and mixtures thereof.
- the prepolymer having the glycidyl ether functional group may include at least one represented by Formulas 1-7 above.
- the prepolymer may also be addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)-1-butanol (which are commercially available under the trade name of EHPH-3150).
- the prepolymer having the glycidyl ether functional group in the negative photoresist composition may be crosslinked by exposure to radiation of actinic ray, e.g., UV light.
- the cationic photoinitiator may be a sulfonium salt or an iodonium salt.
- the solvent may be at least one selected from the group consisting of -butyrolactone, propylene glycol methyl ether acetate (PGMEA), tetrahydrofuran (THF), methyl ethyl ketone, methy isobutyl ketone, cyclopentanone, and mixtures thereof.
- PGMEA propylene glycol methyl ether acetate
- THF tetrahydrofuran
- methyl ethyl ketone methy isobutyl ketone
- cyclopentanone and mixtures thereof.
- an upper surface of a sacrificial layer can be planarized, and thus, it is possible to easily control the shape and dimension of an ink passage, thereby improving uniformity of the ink passage.
- a crosslinked polymer constituting a chamber and a nozzle layer according to the present invention is prepared by crosslinking of a prepolymer that has a plurality of glycidyl ether functional groups and a phenolic novolak resin-based backbone, a bisphenol-A backbone, or an alicyclic-based backbone.
- the glycidyl ether functional groups can be disposed on hydrogen positions of phenolic hydroxy groups.
- a difunctional epoxy resin having two glycidyl ether groups may be represented by Formula 7 below:
- m is an integer ranging from 1 to 25, preferably an integer of 1 to 20.
- the difunctional epoxy resin having two glycidyl ether groups can form a film with a low crosslinking density.
- the content of the difunctional epoxy resin may range from about 5 to about 50% by weight, preferably from about 10 to about 20% by weight, based on the total weight of the negative photoresist composition.
- difunctional epoxy resin having two glycidyl ether groups examples include, but are not limited to, EPON 828, EPON 1004, EPON 1001F, and EPON 1010 (which are commercially obtainable from Shell Chemicals), DER-332, DER-331, and DER-164 (which are commercially obtainable from Dow Chemical Company), and ERL-4201 and ERL-4289 (which are commercially obtainable from Union Carbide Corporation).
- a multifunctional epoxy resin having more than two glycidyl ether groups will now be described.
- the multifunctional epoxy resin having more than two glycidyl ether group can form a film with a high crosslinking density, increasing a resolution and thereby preventing swelling with respect to ink or a solvent.
- the content of the multifunctional epoxy resin may range from about 0.5 to about 20% by weight, preferably from about 1 to about 5% by weight, based on the total weight of the negative photoresist composition.
- Examples of the multifunctional epoxy resin having more than two glycidyl ether groups include, but are not limited to, EPON SU-8 and EPON DPS-164 (which are commercially obtainable from Shell Chemicals), DEN-431 and DEN-439 (which are commercially obtainable from Dow Chemical Company), and EHPE-3150 (which is commercially obtainable from Daicel Chemical Industries, Ltd.).
- Examples of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone include compounds represented by Formula 1 below:
- the prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone may also use o-cresol or p-cresol instead of phenol when designing a backbone structure, as represented by Formulas 2 and 3 below:
- Examples of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a bisphenol-A-based backbone include compounds represented by Formulas 5 and 6 below:
- the number n of the monomer repeating units can range from 1 to about 20, preferably from 1 to about 10.
- Examples of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and an alicyclic-based backbone include addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)1-butanol (which are commercially available under the trade name of EHPH-3150).
- Photoinitiators are compounds that can generate ions or free radicals that initiate polymerization upon exposure to light.
- the content of the photoinitiator may range from about 1.0 to about 10% by weight, preferably from about 1.5 to 5% by weight, based on the total weight of the negative photoresist composition. If the content of the photoinitiator is less than 1.0% by weight, unreacted prepolymers may be left due to insufficient photopolymerization. On the other hand, if the content of the photoinitiator exceeds 10% by weight, energy higher than the energy value corresponding to a film thickness may be needed, and the wall profile of a pattern may be changed.
- suitable photoinitiators include, but are not limited to, aromatic halominum salts and aromatic onium salts of Group VA or VI elements.
- suitable photoinitiators include, but are not limited to, UVI-6974 (which is commercially obtainable from Union Carbide Corporation), SP-172 (which is commercially obtainable from Asahi denka, Co., Ltd.), and on the like.
- aromatic sulfonium salt examples include, but are not limited to, triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate (UVI-6974), phenylmethylbenzylsulfonium hexafluoroantimonate, phenylmethylbenzylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, methyl diphenylsulfonium tetrafluoroborate, and dimethyl phenylsulfonium hexafluorophsophate.
- triphenylsulfonium tetrafluoroborate examples include, but are not limited to, triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate (UVI-6974), phenylmethylbenzylsulfon
- aromatic iodonium salt examples include, but are not limited to, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoroantimonate, and butylphenyl iodonium hexafluoroantimonate (SP-172).
- suitable solvents include, but are not limited to, -butyrolactone, propylene glycol methyl ether acetate (PGMEA), tetrahydrofuran (THF), methyl ethyl ketone, methy isobutyl ketone, and mixtures thereof.
- a suitable content of the solvent can range from about 20 to about 90% by weight, preferably from about 45 to 75% by weight, based on the total weight of the negative photoresist composition.
- photosensitizers As additional additives, photosensitizers, silane coupling agents, fillers, viscosity modifiers, and the like, can be used.
- Sensitizers absorb light energy and facilitate the transfer of energy to another compound, which can then form radical or ionic initiators. Sensitizers frequently expand a useful energy wavelength range for photoexposure, and typically are aromatic light absorbing chromophores. Sensitizers can also lead to the formation of photoinitiators, which can be free radical or ionic forms.
- the sensitizer can be present in an amount of from about 0.1 to about 20% by weight based on the total weight of the negative photoresist composition.
- FIGS. 3A through 3R are cross-sectional views illustrating a method of manufacturing an inkjet printhead using a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol-A-based backbone, or an alicyclic-based backbone according to an embodiment of the present general inventive concept.
- a heater 141 to heat ink and an electrode 142 to supply current to the heater 141 can be formed on a substrate 110 .
- a silicon wafer is used as the substrate 110 in FIGS. 3A-3R .
- a silicon wafer is widely used in manufacturing semiconductor devices and is advantageous for mass production.
- the present general inventive concept is not limited to the substrate 110 being a silicon wafer.
- the heater 141 can be formed by depositing a resistive heating element, such as tantalum-nitride or a tantalum-aluminum alloy, on the substrate 110 by sputtering or chemical vapor deposition (CVD) and patterning the deposited resistive heating element.
- the electrode 142 can be formed by depositing a metal having good conductivity, such as aluminum or an aluminum alloy, on the substrate 110 by sputtering and patterning the deposited metal.
- a passivation layer made of, for example, silicon oxide or silicon nitride, may be formed on the heater 141 and the electrode 142 .
- a first negative photoresist layer 121 can be formed on the substrate 110 where the heater 141 and the electrode 142 are formed.
- the first negative photoresist layer 121 forms a passage forming layer (see 120 of FIG. 3D ) surrounding an ink chamber and a restrictor, which will be described later.
- the first negative photoresist layer 121 can be formed by applying a negative photoresist composition containing a prepolymer having a glycidyl ether functional group to a predetermined thickness to an entire surface of the substrate 110 .
- the negative photoresist composition is as described above.
- the negative photoresist composition may be applied to a thickness substantially corresponding to a height of the ink chamber so as to accommodate the quantity of ink droplets ejected.
- the negative photoresist composition may be applied to the substrate 110 using a spin coating process.
- the first negative photoresist layer 121 can be exposed to an actinic radiation, such as UV light, using a first photomask 161 having a passage forming layer pattern. Specifically, an exposed portion of the first negative photoresist layer 121 can be cured so as to have chemical resistance and high mechanical strength. On the other hand, an unexposed portion of the first negative photoresist layer 121 is easily dissolved in a developer.
- an actinic radiation such as UV light
- the unexposed portion is removed to form a space, and the exposed and cured portion is left to form a passage forming layer 120 , as illustrated in FIG. 3D .
- FIGS. 3E through 3L illustrate the formation of a sacrificial layer S in the space surrounded by the passage forming layer 120 .
- the sacrificial layer S has a planarized upper surface (i.e., the upper surface does not protrude at its peripheral edges, and does not bulge upward around the passage forming layer 120 ).
- the upper surface of the sacrifical layer S can be planarized by applying a positive photoresist, patterning the positive photoresist at least twice, and planarizing the resulting structure once.
- the positive photoresist can be applied to the entire surface of the substrate 110 having thereon the passage forming layer 120 to a predetermined thickness by spin-coating, thereby forming a first sacrificial layer 123 .
- the positive photoresist bulges upward due to the protruding passage forming layer 120 , making the upper surface of the first sacrificial layer 123 uneven.
- the first sacrificial layer 123 can be exposed to UV light using a second photomask 162 having a predetermined pattern covering a region between patterns of the passage forming layer 120 .
- first sacrificial layer 123 a portion of the first sacrificial layer 123 exposed to UV light becomes easily dissolved in a developer.
- first sacrificial layer 123 when the first sacrificial layer 123 is developed, only an unexposed portion of the first sacrificial layer 123 is left while the exposed portion is removed, as illustrated in FIG. 3G .
- a positive photoresist is applied for a second time to the entire surface of the substrate 110 having thereon the passage forming layer 120 and the first sacrificial layer 123 to a predetermined thickness by spin-coating, thereby forming a second sacrificial layer 124 .
- the upper surface of the second sacrificial layer 124 can be planarized by the first sacrificial layer 123 filled in the space surrounded by the passage forming layer 120 .
- the second sacrificial layer 124 can be exposed to UV light using a second photomask 162 , which is identical to the first photomask 162 used to expose the first sacrificial layer 123 . Subsequently, the second sacrificial layer 124 can be developed to remove an exposed portion of the second sacrificial layer 124 . As a result, as illustrated in FIG. 3J , the sacrificial layer S consisting of the first sacrificial layer 123 and the second sacrificial layer 124 and having the planarized upper surface can be formed in a space surrounded by the passage forming layer 120 .
- the sacrificial layer S can be exposed to UV light.
- the exposing may be performed by blank exposure without using a photomask.
- the sacrificial layer S can be continuously exposed so that the upper surface of the sacrificial layer S becomes substantially the same height as that of the passage forming layer 120 by controlling an exposure time and light intensity.
- the sacrificial layer S can be developed to remove the exposed portion of the sacrificial layer S and to lower the height of the sacrificial layer S, so that the sacrificial layer S has substantially the same height as the passage forming layer 120 , as illustrated in FIG. 3L .
- the sacrificial layer S can be formed by applying, exposing, and developing the first sacrificial layer 123 (see FIGS. 3E-3G ), applying, exposing, and developing the second sacrificial layer 124 (see FIGS. 3H-3J ), and then performing blank exposure and development (see FIGS. 3K-3L ), the sacrificial layer S may be formed differently from the above-described formation.
- the application of the second sacrificial layer 124 may be followed by performing blank exposure (as opposed to the exposure through the second photomask 162 illustrated in FIG. 3I ).
- the sacrificial layer S may be formed as described below.
- the second sacrificial layer 124 can be applied and exposed using the second photomask 162 and using blank exposure.
- the sequence of exposing using the second photomask 162 and using blank exposure may be reversed. That is, the applied second sacrificial layer 124 can be exposed using blank exposure followed by exposure using the second photomask 162 .
- the exposed portion is removed by development, so that only the sacrificial layer S surrounded by the passage forming layer 120 remains.
- the positive photoresist is applied twice in order to form a sacrificial layer S having a planarized upper surface
- the positive photoresist may be applied three or more times until the sacrificial layer S has a desired thickness. In this case, the number of times of performing exposure and development increases according to the number of times of applying positive photoresist.
- a second negative photoresist layer 131 can be formed on the substrate 110 where the passage forming layer 120 and the sacrificial layer S are formed. Since the second negative photoresist layer 131 forms a nozzle layer (see 130 FIG. 3O ), which will be described later, the second negative photoresist layer 131 can be formed of a material that is chemically stable against ink, like the passage forming layer 120 . For this, the second negative photoresist layer 131 can be formed by applying a composition containing a prepolymer having a glycidyl ether functional group to an entire surface of the substrate 110 to a predetermined thickness by spin coating.
- composition containing the prepolymer having the glycidyl ether functional group may be applied to a thickness enough to obtain a sufficiently long nozzle and to withstand a change in the pressure of the ink chamber upon formation of the second negative photoresist layer 131 .
- the sacrificial layer S is formed to have substantially the same height as the passage forming layer 120 , that is, the upper surface of the sacrificial layer S is planarized, it is possible to overcome the deformation or melting problem that occurs in the prior art, as discussed above. In particular, the deformation or melting of edges of the sacrificial layer S due to a reaction between the positive photoresist forming the sacrificial layer S and the material forming the second negative photoresist layer 131 that occurs in the prior art is avoided. Thus, the second negative photoresist layer 131 can be suitably adhered to the passage forming layer 120 .
- the second negative photoresist layer 131 is exposed using a third photomask 163 having a nozzle pattern. Subsequently, when the second negative photoresist layer 131 is developed, the unexposed portion is removed to form a nozzle 154 , and the exposed and cured portion is left to form a nozzle layer 130 , as illustrated in FIG. 3O .
- Actinic radiation can be used to expose the second negative photoresist layer 131 . Specifically, a UV beam of not longer than an I-line radiation (353 nm), H-line radiation (405 nm), and G-line radiation (436 nm), or an e-beam or X-ray having wavelengths shorter than an I-line radiation can be used.
- exposing by using light having a relatively short wavelength shortens a transmission length of light, so that the sacrificial layer S disposed under the second negative photoresist layer 131 is not affected by exposure.
- nitrogen gas is not generated in the sacrificial layer S formed of the positive photoresist, thereby avoiding deformation of the nozzle layer 130 due to nitrogen gas.
- an etch mask 171 to form an ink supply hole 151 can be formed on a rear surface of the substrate 110 .
- the etch mask 171 is formed by applying a positive or negative photoresist to the rear surface of the substrate 110 and patterning the same.
- the substrate 110 exposed by the etch mask 171 can be etched from the rear surface thereof to be perforated, thereby forming an ink supply hole 151 , followed by removing the etch mask 171 .
- the etching of the rear surface of the substrate 110 may be performed by dry etching using, for example, plasma.
- the rear surface of the substrate 110 may be etched by wet etching using, for example, tetramethylammonium hydroxide (TMAH) or KOH as an etchant.
- TMAH tetramethylammonium hydroxide
- KOH tetramethylammonium hydroxide
- the sacrificial layer S can be removed using a solvent, thereby forming an ink chamber 153 and a restrictor 152 surrounded by the passage forming layer 120 in a space without the sacrificial layer S, as illustrated in FIG. 3R .
- an inkjet printhead having the structure illustrated in FIG. 3R is completed.
- a step difference between the ink chamber 153 of the inkjet printhead and the sacrificial layer S is not greater than 3 ⁇ m.
- FIGS. 4A through 4F are cross-sectional views illustrating a method of manufacturing an inkjet printhead according to another embodiment of the present general inventive concept.
- the same portions as those described above with respect to the embodiment illustrated in FIGS. 3A-3N will be briefly described or omitted for the sake of brevity.
- a sacrificial layer S is formed on a substrate 210 in substantially the same manner as illustrated in FIGS. 3A through 3J , which will now be described briefly.
- the substrate 210 is prepared and a heater 241 to heat ink and an electrode 242 to supply current to the heater 241 are formed on the substrate 210 .
- a negative photoresist composition containing a prepolymer having a glycidyl ether functional group is applied to the substrate 210 having thereon the heater 241 and the electrode 242 to a predetermined thickness, followed by exposing and developing the negative photoresist composition, thereby forming a passage forming layer 220 which is a first negative photoresist layer.
- the passage forming layer 220 may be formed to be slightly lower than an ink chamber having a desired height.
- a positive photoresist composition is applied to an entire surface of the substrate 210 having thereon the passage forming layer 220 to a predetermined thickness by spin-coating, thereby forming a first sacrificial layer 223 , and the applied positive photoresist composition is exposed and developed.
- the positive photoresist composition is applied a second time to the entire surface of the substrate 210 to a predetermined thickness by spin-coating, thereby forming a second sacrificial layer 224 , and the twice applied positive photoresist composition is exposed and developed.
- the sacrificial layer S having the first and second sacrificial layers 223 and 224 and having a planarized upper surface is formed in a space surrounded by the passage forming layer 220 , as illustrated in FIG. 4A .
- an imide-based positive photoresist can be used as the positive photoresist, and blank exposure and development therefore do not need to be performed.
- the imide-based positive photoresist is used as the positive photoresist, the height of the sacrificial layer S does not need to be made substantially equal to that of the passage forming layer 220 .
- the imide-based positive photoresist should be subjected to hard baking at approximately 140° C. after being developed. However, the imide-based positive photoresist is not affected by a solvent contained in the negative photoresist composition and does not result in the generation of nitrogen gas even upon exposure, which will be described later in more detail.
- a second negative photoresist layer 231 is formed on the substrate 210 having thereon the passage forming layer 220 and the sacrificial layer S. Since the second negative photoresist layer 231 forms a nozzle layer (see 230 of FIG. 4D ), which will be described later, the second negative photoresist layer 231 should be chemically stable against ink. For this, the second negative photoresist layer 231 is formed to a predetermined thickness on the entire surface of the substrate 210 by a spin-coating process using a composition containing a prepolymer having a glycidyl ether functional group as described above. The second negative photoresist layer 231 can be formed as described above for the second negative photoresist layer 131 .
- the sacrificial layer S can be formed to protrude higher than the passage forming layer 220 .
- the sacrificial layer S is formed of the imide-based positive photoresist, it is not affected by a solvent contained in the second negative photoresist layer 231 , as described above.
- the deformation or melting problem occurring at edges of the sacrificial layer S can be avoided.
- the second negative photoresist layer 231 can be exposed using a photomask 263 having a nozzle pattern. Subsequently, when the second negative photoresist layer 231 is developed, an unexposed portion of the second negative photoresist layer 231 is removed to form a nozzle 254 , while the exposed and cured portion is left to form a nozzle layer 230 , as illustrated in FIG. 4D .
- a UV beam over a broadband including I-line radiation (353 nm), H-line radiation (405 nm), and G-line radiation (436 nm), or e-beam or X-ray having wavelengths shorter than the broadband radiations, may be used.
- an etch mask 271 can be formed on a rear surface of the substrate 210 , and the substrate 210 exposed by the etch mask 271 is etched from the rear surface thereof to be perforated by dry etching or wet etching, thereby forming an ink supply hole 251 .
- Specific steps for forming the etch mask 271 and the ink supply hole 251 are the same as those illustrated in FIGS. 3P-3Q .
- the sacrificial layer S can be removed using a solvent, thereby forming an ink chamber 253 and a restrictor 252 surrounded by the passage forming layer 220 in a space obtained by the removal of the sacrificial layer S, as illustrated in FIG. 4F .
- an inkjet printhead having the structure illustrated in FIG. 4F is completed.
- a step difference between the chamber layer of the inkjet printhead and the sacrificial layer is not greater than 3 ⁇ m.
- FIGS. 6A through 6L are sectional views illustrating a method of manufacturing an inkjet printhead, including forming a passage forming layer and a nozzle layer using a negative photoresist composition including a prepolymer as described above and planarizing a sacrificial layer using a chemical mechanical polishing (CMP) process.
- CMP chemical mechanical polishing
- a heater 341 for heating ink and an electrode 342 for supplying current to the heater 341 are formed on a substrate 310 .
- a silicon wafer may be used as the substrate 310 .
- the silicon wafer is widely used to manufacture semiconductor devices and is effective for mass production.
- the heater 341 can be formed by depositing a resistive heating element, such as tantalum-nitride or a tantalum-aluminum alloy, on the substrate 310 by sputtering or chemical vapor deposition (CVD) and patterning the deposited resistive heating element.
- the electrode 342 can be formed by depositing a metal having good conductivity, such as aluminum or an aluminum alloy, on the substrate 310 by sputtering and patterning the deposited metal.
- a passivation layer made of silicon oxide or silicon nitride may be formed on the heater 341 and the electrode 342 .
- a first negative photoresist layer 321 is formed on the substrate 310 having thereon the heater 341 and the electrode 342 .
- the first negative photoresist layer 321 becomes a passage forming layer (see 320 of FIG. 6D ) defining an ink passage including an ink chamber and a restrictor in a subsequent step as will be described later.
- the first negative photoresist layer 321 is crosslinked by radiation of actinic ray, such as UV light, and thus, is chemically stabilized against ink.
- the first negative photoresist layer 321 may be made of a composition containing a prepolymer having a glycidyl ether functional group on monomer repeating units as described above.
- the first negative photoresist layer 321 is formed by coating the composition to a predetermined thickness on the entire surface of the substrate 310 .
- the composition may be coated on the substrate using a spin coating process.
- the first negative photoresist layer 321 is exposed to UV light using a first photomask 361 having ink chamber and restrictor patterns.
- a portion of the first negative photoresist layer 321 exposed to UV light is cured and thus develops a chemical resistance and a high mechanical strength.
- an unexposed portion of the first negative photoresist layer 321 is easily dissolved in a developer.
- a passage forming layer 320 defining an ink passage is formed.
- a sacrificial layer S is formed on the substrate 310 so as to cover the passage forming layer 320 .
- the sacrificial layer S is formed to have a higher height than the passage forming layer 320 .
- the sacrificial layer S may be formed by coating a positive photoresist or a non-photosensitive soluble polymer to a predetermined thickness on the substrate 310 using a spin coating process.
- the positive photoresist may be an imide-based positive photoresist.
- the sacrificial layer S is made of an imide-based positive photoresist, it is hardly affected by a solvent, and does not generate a nitrogen gas upon exposure to light.
- the sacrificial layer S may also be formed by coating a liquid non-photosensitive soluble polymer to a predetermined thickness on the substrate 310 using a spin coating process and baking the soluble polymer.
- the soluble polymer may be at least one selected from the group consisting of a phenolic resin, a polyurethane resin, an epoxy resin, a polyimide resin, an acrylic resin, a polyamide resin, an urea resin, a melamine resin, and a silicon resin.
- upper surfaces of the passage forming layer 320 and the sacrificial layer S are planarized using a CMP process.
- the upper surfaces of the sacrificial layer S and the passage forming layer 320 are polished by a CMP process to reach a desired height for the ink passage, the upper surfaces of the passage forming layer 320 and the sacrificial layer 160 are formed at substantially the same height.
- a second negative photoresist layer 331 is formed on the passage forming layer 320 and the sacrificial layer S that have been planarized.
- the second negative photoresist layer 331 may be formed using a composition containing a prepolymer having a glycidyl ether functional group on monomer repeating units as described above, like the first negative photoresist layer 321 .
- the second negative photoresist layer 331 becomes a nozzle layer (see 330 of FIG. 6I ) in a subsequent process as will be described later.
- the second negative photoresist layer 331 is crosslinked by radiation of actinic ray, such as UV light, and thus, is chemically stabilized against ink.
- the second negative photoresist layer 331 is formed by coating the composition to a predetermined thickness on the passage forming layer 320 and the sacrificial layer S using a spin coating process.
- the second negative photoresist layer 331 is coated to have a thickness such that a sufficient nozzle length can be ensured and pressure variations in an ink chamber can be endured.
- the sacrificial layer S and the passage forming layer 320 are planarized to have the same heights, transformation or melting of an edge portion of the sacrificial layer S, which may be caused due to reaction between the material forming the second negative photoresist layer 331 and the material forming the sacrificial layer S, does not occur. Therefore, the second photoresist layer 331 can be closely adhered to the upper surface of the passage forming layer 320 .
- the second negative photoresist layer 331 is exposed using a second photomask 363 having a nozzle pattern. Then, when the second negative photoresist layer 331 is developed, an unexposed portion of the second negative photoresist layer 331 is removed to form a nozzle 354 , and an exposed and cured portion of the second negative photoresist layer 331 is left to form a nozzle layer 330 , as illustrated in FIG. 6I .
- the sacrificial layer S is made of an imide-based positive photoresist as described above, a nitrogen gas is not generated even though exposure-light reaches the sacrificial layer S beyond the second negative photoresist layer 331 . Therefore, deformation of the nozzle layer 330 due to a nitrogen gas can be prevented.
- an etch mask 371 for forming an ink feed hole (see 351 of FIG. 6K ) is formed on a rear surface of the substrate 310 .
- the etch mask 371 may be formed by coating a positive or negative photoresist on the rear surface of the substrate 310 and patterning the photoresist.
- a rear surface of the substrate 310 exposed through the etch mask 371 is etched so as to penetrate the substrate 310 to thereby form an ink feed hole 351 .
- the etch mask 371 is removed.
- the etching of the rear surface of the substrate 310 may be performed by a dry etching process using plasma.
- the etching of the rear surface of the substrate 310 may also be performed by a wet etching process using tetramethylammonium hydroxide (TMAH) or KOH as an etchant.
- TMAH tetramethylammonium hydroxide
- a commercial resist solution of EPON SU-8 was obtained from MicroChem. Corp., and was used as received.
- the commercial solution included -butyrolactone contained in an amount between 25 and 50% by weight, and a mixture of triarylsulfonium hexafluoroantimonate and p-thiophenoxyphenyldiphenysulfonium hexafluoroantimonate in propylene carbonate contained in an amount between 1 and 5% by weight.
- a tantalum nitride heater pattern and an electrode pattern made of AlSiCu alloy (the content of each of Si and Cu was 1% by weight or less) were each formed to a thickness of about 500 ⁇ on a 6-inch silicon wafer using a sputtering process and a photolithography process commonly known in the art (see FIG. 3A ).
- the resist composition 1 was spin-coated on the entire surface of the silicon wafer having thereon the heater pattern and the electrode pattern at a speed of 2000 rpm for 40 seconds and baked at 95° C. for seven minutes to form a first negative photoresist layer with a thickness of about 10 ⁇ m.
- the first negative photoresist layer was exposed to UV light of I-line using a first photomask having predetermined ink chamber and restrictor patterns. At this time, the exposure dose was adjusted to 130 mJ/cm 2 .
- the wafer was baked at 95° C. for three minutes, dipped in a PGMEA developer for one minute for development, and rinsed with isopropanol for 20 seconds, to complete a passage forming layer pattern (see 120 of FIG. 3D ).
- An imide-based positive photoresist (trade name: PW-1270, manufactured by TORAY) was spin-coated on the entire surface of the wafer having thereon the passage forming layer pattern at a speed of 1000 rpm for 40 seconds, and baked at about 140° C. for 10 minutes to form a first sacrificial layer (see 123 of FIG. 3E ).
- the thickness of the first sacrificial layer was adjusted such that the overcoat thickness of the first sacrificial layer on the passage forming layer pattern was about 5 ⁇ m.
- the first sacrificial layer was exposed to UV light of I-line using a second photomask having predetermined pattern covering region between the passage forming layer pattern. At this time, the exposure dose was adjusted to 130 mJ/cm 2 . Then, the wafer was baked at 95° C. for three minutes, dipped in a developer (AZ300K, manufactured by Clariant) for one minute for development, and rinsed with isopropanol for 20 seconds. This completed first sacrificial layer (see 123 of FIG. 3G ).
- AZ300K manufactured by Clariant
- An imide-based positive photoresist was spin-coated on the entire surface of the wafer having thereon the passage forming layer pattern and the first sacrificial layer, baked, exposed to light, baked (post-exposure bake), developed, and rinsed in the same manner as in the formation of the first sacrificial layer to form second sacrificial layer (see 124 of FIG. 3J ).
- the sacrificial layer including the first sacrificial layer and the second sacrificial layer and having planarized upper surface was formed in space surrounded by the passage forming layer pattern.
- the sacrificial layers were subjected to blank exposure to UV light of 1-line at an exposure dose of 260 mJ/cm 2 such that the UV light reached a portion of the sacrificial layer that was the same level as the upper surface of the passage forming layer pattern. Then, the sacrificial layer was subjected to post-exposure bake, development, and rinsing to remove the exposed portion of the sacrificial layer so that the height of the sacrificial layer was equal to that of the passage forming layer pattern (see FIG. 3I ).
- a nozzle layer pattern was formed on the silicon wafer having thereon the passage forming layer pattern and the sacrificial layer using the resist composition 1 and a third photomask having a predetermined nozzle pattern under the same conditions as the formation of the passage forming layer pattern (see FIGS. 3N and 3O ).
- etch mask was formed on rear surface of the silicon wafer using a photolithography process commonly known in the art to form ink feed hole. Then, as illustrated in FIG. 3Q , the rear surface of the silicon wafer exposed through the etch mask was etched using a plasma etching process to form ink feed hole, and the etch mask was then removed. At this time, an etching power of a plasma etching apparatus was adjusted to 2000 Watt, an etching gas was a mixture gas of SF 6 and O 2 (mixture ratio: 10:1 by volume), and an etch rate was 3.7 ⁇ m/min.
- FIGS. 5A and 5B are vertical sectional views illustrating inkjet printhead manufactured according to the above-described method. Referring to FIGS. 5A and 5B , a cavity is not formed between a passage forming layer 120 and a nozzle layer 130 , which suggests that the passage forming layer 120 and the nozzle layer 130 are firmly adhered to each other.
- This Example is intended to specifically describe a method of manufacturing an inkjet printhead, including forming a passage forming layer and a nozzle layer using a negative photoresist composition including a prepolymer as described above and planarizing a sacrificial layer using a CMP process.
- a tantalum nitride heater pattern, an AlSiCu alloy electrode pattern, and a passage forming layer pattern were formed on a 6-inch silicon wafer in the same manner as in Example 1 (see FIGS. 6A through 6D ).
- an imide-based positive photoresist was spin-coated on the entire surface of the wafer having thereon the passage forming layer pattern at a speed of 1000 rpm for 40 seconds, and baked at about 140° C. for 10 minutes to form sacrificial layer.
- the thickness of the sacrificial layer was adjusted such that the overcoat thickness of the sacrificial layer on the passage forming layer pattern was about 5 ⁇ m.
- the wafer was supplied onto a polishing pad (Model No.: JSR FP 8000, manufactured by JSR) of a polishing plate such that the sacrificial layer faced the polishing pad. Then, the wafer was pressed onto the polishing pad, under a pressure of 10 ⁇ 15 kPa with a backing pad, by a press head. While polishing slurries (FUJIMI Corporation, POLIPLA 103) were supplied onto the polishing pad, the press head was rotated with respect to the polishing plate.
- a polishing pad Model No.: JSR FP 8000, manufactured by JSR
- the rotation speed of each of the press head and the polishing pad was 40 rpm.
- the backing pad was made of a material whose Shore D hardness was 30 ⁇ 70.
- the sacrificial layer was planarized at an etch rate of 5-7 ⁇ m/min until upper surface of the passage forming layer pattern was removed by a thickness of about 1 ⁇ m.
- FIGS. 7A and 7B Images of the passage forming layer pattern and the sacrificial layer after the CMP process are shown in FIGS. 7A and 7B .
- the upper surfaces of the passage forming layer pattern and the sacrificial layer were planarized by the CMP process.
- FIGS. 8A and 8B are vertical sectional images of inkjet printhead manufactured as described in Example 2.
- an ink chamber 353 and a restrictor 352 are formed to have substantially equal heights, and no cavity is generated between a passage forming layer 320 and a nozzle layer 330 .
- the nozzle layer 330 is firmly adhered to an upper surface of the passage forming layer 320 .
- a shape and dimension of an ink passage can be easily controlled, thereby improving a uniformity of the ink passage, ultimately improving ink ejection performance of the inkjet printhead.
- a passage forming layer and a nozzle layer are suitably adhered to each other, durability of the printhead is enhanced.
- nitrogen gas is not generated in the sacrificial layer during photography to form a nozzle, deformation of the nozzle layer due to nitrogen gas can be avoided. Accordingly, uniformity of the ink passage can be further enhanced.
Abstract
Description
- The present application is a continuation-in-part application of co-pending U.S. patent application Ser. No. 11/415,198, entitled, “METHOD OF MANUFACTURING INKJET PRINTHEAD USING CROSSLINKED POLYMER”, which was filed on May 2, 2006 and claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 2005-39712, filed on May 12, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
- 1. Field of the Invention
- The present general inventive concept relates to a method of manufacturing an inkjet printhead, and more particularly, to a method of manufacturing an inkjet resist composition printhead by photolithography using a crosslinked polymer.
- 2. Description of the Related Art
- In general, inkjet printheads are devices for printing a predetermined color image by ejecting small droplets of printing ink at a desired position on a recording sheet. Ink ejection mechanisms of an inkjet printer are generally categorized into two different types: a thermally driven type (bubble-jet type), in which a heat source is employed to form bubbles in ink thereby causing an ink droplet to be ejected, and an piezoelectrically driven type, in which an ink droplet is ejected by a change in ink volume due to deformation of a piezoelectric element.
- A typical structure of a conventional thermally-driven inkjet printhead is illustrated in
FIG. 1 . Referring toFIG. 1 , the inkjet printhead includes asubstrate 10, apassage forming layer 20 stacked on thesubstrate 10, and anozzle plate 30 formed on thepassage plate 20. Anink supply hole 51 is formed in thesubstrate 10. Thepassage forming layer 20 has anink chamber 53 to store ink and arestrictor 52 connecting theink supply hole 51 and theink chamber 53. Thenozzle layer 30 has anozzle 54 through which the ink is ejected from theink chamber 53. Also, thesubstrate 10 has aheater 41 for heating ink in theink chamber 53 and anelectrode 42 for supplying current to theheater 41. - The ink ejection mechanism of the conventional thermally-driven inkjet printhead having the above-described configuration will now be described. Ink is supplied from an ink reservoir (not illustrated) to the
ink chamber 53 through theink supply hole 51 and therestrictor 52. The ink filling theink chamber 53 is heated by aheater 41 consisting of resistive heating elements. The ink boils to form bubbles and the bubbles expand so that the ink in theink chamber 53 is ejected by a bubble pressure. Accordingly, the ink in theink chamber 53 is ejected outside theink chamber 53 through thenozzle 54 in the form of ink droplets. - The conventional thermally-driven inkjet printhead having the above-described configuration can be monolithically manufactured by photolithography, and the photolithography manufacturing process thereof is illustrated in
FIGS. 2A through 2E . - Referring to
FIG. 2A , asubstrate 10 having a predetermined thickness is prepared, and aheater 41 for heating ink and anelectrode 42 for supplying a current to theheater 41 are formed on thesubstrate 10. - As illustrated in
FIG. 2B , a negative type photoresist composition is applied to the entire surface of thesubstrate 10 to a predetermined thickness and the negative type photoresist composition is then patterned in such a shape as to surround an ink chamber 53 (seeFIG. 2E ) and a restrictor 52 (seeFIG. 2E ) by photolithography, thereby forming apassage forming layer 20. - As illustrated in
FIG. 2C , a space surrounded by thepassage forming layer 20 is filled with a positive-type photoresist composition, thereby forming a sacrificial layer S. In detail, the positive-type photoresist composition is applied to the entire surface of thesubstrate 10 to a predetermined thickness and the positive-type photoresist composition is then patterned, thereby forming a sacrificial layer S. Here, the positive-type photoresist composition is generally applied by spin coating, and the top surface of the applied positive-type photoresist is not planarized (i.e., has an uneven surface, as illustrated inFIGS. 2C and 2D ) due to the centrifugal force of the spin coating. In other words, the positive-type photoresist bulges upward around thepassage forming layer 20 due to the centrifugal force provided during spin coating, as indicated by the double-dashed line illustrated inFIG. 2C . If the uneven surface of the positive-type photoresist is patterned, the sacrificial layer S protrudes upward at its peripheral edges, as illustrated inFIG. 2D . - As illustrated in
FIG. 2D , a negative type photoresist composition is applied to thepassage forming layer 20 and the sacrificial layer S to a predetermined thickness and the negative type photoresist composition is then patterned by photolithography, thereby forming anozzle layer 30 having anozzle 54. - Subsequently, as illustrated in
FIG. 2E , the bottom surface of thesubstrate 10 is wet-etched to form anink supply hole 51, and the sacrificial layer S is removed through theink supply hole 51, thereby forming therestrictor 52 and theink chamber 53 in thepassage forming layer 20. - Referring back to
FIG. 2D , when forming thenozzle layer 30 by applying a crosslinked polymer resist composition to the sacrificial layer S, a projecting edge of the sacrificial layer S made of the positive-type photoresist may react with a solvent contained in the crosslinked polymer resist composition, causing deformation or melting. Then, as illustrated inFIG. 2E , a cavity C is formed between thepassage forming layer 20 and thenozzle layer 30. Furthermore, thepassage forming layer 20 and thenozzle layer 30 are not suitably adhered to each other due to existence of the cavity C formed between thepassage forming layer 20 and thenozzle layer 30. - As described above, according to the conventional manufacturing method of an inkjet printhead, since the shape and dimension of an ink passage are not easily controlled, it is difficult to attain uniformity of the ink passage, and an ink ejection performance of the printhead may deteriorate. Further, since the
passage forming layer 20 and thenozzle layer 30 are not suitably adhered to each other, the durability of the inkjet printhead is lowered. - Referring back to
FIG. 2D , the crosslinked polymer resist composition applied to the sacrificial layer S is patterned by exposure, development, and baking. During the exposure, broadband UV light, including I-line (353 nm), H-line (405 nm), and G-line (436 nm), is usually used. Here, the H-line and the G-line, each having a relatively long wavelength and a long penetration depth, affect both the crosslinked polymer resist composition forming thenozzle layer 30 and the positive photoresist forming the sacrificial layer S disposed under thenozzle layer 30. Also, when the positive photoresist is irradiated with UV light, a photosensitizer contained therein may be decomposed by the light, producing nitrogen (N2) gas. The produced nitrogen gas expands during baking to lift thenozzle layer 30, resulting in deformation of thenozzle layer 30. - The present general inventive concept provides a method of manufacturing an inkjet printhead that can easily control a shape and dimension of an ink passage by planarizing a top surface of a sacrificial layer, thereby improving uniformity of the ink passage, and an inkjet printhead manufactured by the method.
- The present general inventive concept provides an inkjet printhead having a planarized surface of a sacrificial layer to control a shape and a dimension of an ink passage, thereby improving uniformity of the ink passage and preventing deformation of a nozzle layer due to gas generated in the sacrificial layer.
- Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.
- The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing a method of manufacturing an inkjet printhead, the method including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; applying a negative photoresist composition to the substrate having thereon the heater and the electrode and patterning the negative photoresist composition to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying the negative photoresist composition to the passage forming layer and the sacrificial layer and patterning the negative photoresist composition to form a nozzle layer having a nozzle; etching a rear surface of the substrate to form an ink supply hole; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The monomers in the prepolymer can all have an identical formula. The monomers in the prepolymer can all have different formulas. The monomers in the prepolymer can include a mixture of some of the monomers having an identical formula and others of the monomers having different formulas.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet printhead manufactured by the method.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a method of manufacturing an inkjet printhead, the method including: applying a first negative photoresist composition to a substrate having thereon a heater and an electrode; patterning the first negative photoresist composition to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying a second negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the passage forming layer and the sacrificial layer; patterning the second negative photoresist composition to form a nozzle layer having a nozzle; and removing the sacrificial layer.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a method of manufacturing an inkjet printhead, the method including: applying to a substrate a negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone; exposing the negative photoresist composition applied to the substrate to ultraviolet light to form a first crosslinked polymer; developing the first crosslinked polymer; applying a positive photoresist composition to the substrate and the first crosslinked polymer; exposing the positive photoresist composition applied to the substrate and the first crosslinked polymer to ultraviolet light to form a first sacrificial layer; developing the first sacrificial layer; applying the positive photoresist composition to the substrate, the first crosslinked polymer, and the first sacrificial layer; exposing the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first sacrificial layer to ultraviolet light to form a second sacrificial layer having a planarized upper surface; and developing the second sacrificial layer.
- The exposing of the negative photoresist composition applied to the substrate may include exposing the negative photoresist composition through a first photomask having a passage forming layer pattern to ultraviolet light to form the first crosslinked polymer. The exposing of the positive photoresist composition applied to the substrate and the first crosslinked polymer may include exposing the positive photoresist composition through a second photomask having an ink chamber pattern to ultraviolet light to form the first sacrificial layer. The exposing of the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first sacrificial layer may include exposing the positive photoresist composition through a second photomask having an ink chamber pattern to ultraviolet light to form the second sacrificial layer having a planarized upper surface.
- The method may further include repeatedly blank exposing the second sacrificial layer having the planarized upper surface until a height of the second sacrificial layer is substantially equal to a height of the passage forming layer, developing the blank exposed second sacrificial layer, applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the substrate and the second sacrificial layer, exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to ultraviolet light to form a second crosslinked polymer, and developing the second crosslinked polymer. The exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer may include exposing the negative photoresist composition through a third photomask having a nozzle layer pattern to ultraviolet light to form the second crosslinked polymer. The method may further include applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic backbone to the substrate and the second sacrificial layer, exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to ultraviolet light to form a second crosslinked polymer, and developing the second crosslinked polymer, in which the positive photoresist composition is an imide-based positive photoresist composition. The exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer can include exposing the negative photoresist composition through a third photomask having a nozzle layer pattern to ultraviolet light to form the second crosslinked polymer.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a photolithography method, including applying a first negative photoresist composition to a substrate having a heater and an electrode formed thereon, patterning the negative photoresist composition to form a passage forming layer, applying a positive photoresist composition to a location on the substrate surrounded by the passage forming layer, patterning the positive photoresist composition to form a sacrificial layer, applying a second negative photoresist composition including a prepolymer that a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the passage forming layer and the sacrificial layer, patterning the second negative photoresist composition to form a nozzle having a nozzle layer, and removing the sacrificial layer. The first negative photoresist composition may include a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone. The positive photoresist composition can be an imide-based positive photoresist composition.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet printhead including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a nozzle layer, disposed on the passage forming layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- A height of the ink chamber can be substantially equal to a height of the passage forming layer. A height of the ink chamber can be greater than a height of the passage forming layer. The passage forming layer can include a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; and a first crosslinked polymer resist layer, disposed on the substrate, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenol novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a sacrificial layer having a planarized upper surface disposed on a portion of the substrate substantially surrounded by the passage forming layer.
- The passage forming layer can include a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone. The sacrificial layer can include an imide-based positive photoresist composition. A height of the sacrificial layer can be substantially equal to a height of the passage forming layer. A height of the sacrificial layer can be greater than a height of the passage forming layer. The inkjet printhead intermediate can further include a polymer layer, disposed on the sacrificial layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet printhead including: a substrate having a passage, at least one heater formed on a first portion of the substrate, at least one electrode formed on a second portion of the substrate, a passage forming layer formed on a third portion of the substrate, and a nozzle layer formed on the passage forming layer, having a planarized surface facing the substrate. The surface of the nozzle layer and a surface of the passage forming layer can form an angle without a cavity on at least one of the surfaces of the nozzle layer and the passage forming layer.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a method of manufacturing an inkjet printhead, including forming a substrate having a passage, forming at least one heater on a first portion of the substrate, forming at least one electrode on a second portion of the substrate, forming a passage forming layer on a third portion of the substrate, and forming a nozzle layer having a planarized surface facing the substrate on the passage forming layer. The forming of the nozzle layer having the planarized surface facing the substrate on the passage forming layer can include forming an angle without a cavity between the surface of the nozzle layer and a surface of the passage forming layer.
- The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a method of manufacturing an inkjet printhead, the method including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; coating a negative photoresist composition on the substrate having thereon the heater and the electrode and patterning the negative photoresist composition using a photolithography process to form a passage forming layer that defines an ink passage; forming a sacrificial layer on the substrate having thereon the passage forming layer so as to cover the passage forming layer; planarizing upper surfaces of the passage forming layer and the sacrificial layer using a polishing process; coating a negative photoresist composition on the passage forming layer and the sacrificial layer and patterning the negative photoresist composition using a photolithography process to form a nozzle layer having a nozzle; forming an ink feed hole in the substrate; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The polishing process may be a chemical mechanical polishing (CMP) process. The substrate may be a silicon wafer.
- According to the present invention, an upper surface of a sacrificial layer can be planarized, and thus, it is possible to easily control the shape and dimension of an ink passage, thereby improving uniformity of the ink passage. Moreover, no gas is generated in the sacrificial layer, thereby avoiding deformation of a nozzle layer.
- These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
-
FIG. 1 is a schematic perspective view illustrating a structure of a conventional thermally-driven inkjet printhead; -
FIGS. 2A through 2E are cross-sectional views illustrating a method of manufacturing the conventional inkjet printhead illustrated inFIG. 1 ; -
FIGS. 3A through 3R are cross-sectional views illustrating a method of manufacturing an inkjet printhead according to an embodiment of the present general inventive concept; -
FIGS. 4A through 4F are cross-sectional views illustrating a method of manufacturing inkjet printhead according to an embodiment of the present general inventive concept; and -
FIG. 5A is a vertical cross-sectional view of an inkjet printhead according to an embodiment of the present general inventive concept, andFIG. 5B is an enlarged view illustrating the vertical cross-sectional view inFIG. 5A ; -
FIGS. 6A through 6L are sectional views illustrating a method of manufacturing an inkjet printhead according to an embodiment of the present invention; -
FIGS. 7A and 7B are images showing a passage forming layer and a sacrificial layer after a chemical mechanical polishing (CMP) process in a method of manufacturing an inkjet printhead according to an embodiment of the present invention; and -
FIGS. 8A and 8B are vertical sectional views illustrating an inkjet printhead manufactured by a method of manufacturing an inkjet printhead according to an embodiment of the present invention. - Korean Patent Application No. 2005-39712, filed on May 12, 2005, in the Korean Intellectual Property Office, and entitled: “METHOD OF MANUFACTURING INKJET PRINTHEAD USING CROSSLINKED POLYMER” is incorporated by reference herein in their entirety.
- Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.
- The present general inventive concept provides a method of manufacturing an inkjet printhead, the method including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; applying a negative photoresist composition to the substrate having thereon the heater and the electrode and patterning the negative photoresist composition to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying the negative photoresist composition to the passage forming layer and the sacrificial layer and patterning the negative photoresist composition to form a nozzle layer having a nozzle; etching a rear surface of the substrate to form an ink supply hole; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group (hereinafter, referred to as simply “glycidyl ether functional group”) on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- In embodiments, the negative photoresist composition may include the prepolymer, a cationic photoinitiator, and a solvent.
- The prepolymer of the negative photoresist composition may form a crosslinked polymer by exposing the prepolymer to an actinic radiation.
- The prepolymer may be prepared from a backbone monomer unit selected from the group consisting of phenol, o-cresol, p-cresol, bisphenol-A, an alicyclic compound, and mixtures thereof.
-
- In each of the above structural Formulas 1-7, m is an integer ranging from 1 to 20, and n is an integer ranging from 1 to 20. The prepolymer may also be addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)-1-butanol (which are commercially available under the trade name of EHPH-3150).
- The cationic photoinitiator can be, for example, a sulfonium salt or an iodonium salt.
-
- According to an embodiment of the present general inventive concept, an inkjet printhead can be manufactured by a method including applying a first crosslinked polymer resist composition to a substrate having a heater and an electrode and patterning the first crosslinked polymer resist composition to form a passage forming layer that surrounds an ink passage, patterning the substrate having the passage forming layer by photolithography at least twice, forming a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer, applying a second crosslinked polymer resist composition to the passage forming layer and the sacrificial layer and patterning the second crosslinked polymer resist composition to form a nozzle layer having a nozzle, and removing the sacrificial layer.
- In embodiments, a step difference between a chamber layer of the inkjet printhead and the sacrificial layer is not greater than about 3 μm.
- Monomers forming the prepolymer can all have an identical formula. The monomers forming the prepolymer can all have different formulas. The monomers forming the prepolymer can include a mixture of some of monomers having an identical formula and others of monomers having different formulae.
- The present general inventive concept also provides a method of manufacturing an inkjet printhead, the method including: applying to a substrate a negative photoresist composition including a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone; exposing the negative photoresist composition applied to the substrate to ultraviolet (UV) light to form a first crosslinked polymer; developing the first crosslinked polymer; applying a positive photoresist composition to the substrate and the first crosslinked polymer; exposing the positive photoresist composition applied to the substrate and the first crosslinked polymer to UV light to form a first sacrificial layer; developing the first sacrificial layer; applying the positive photoresist composition to the substrate, the first crosslinked polymer, the first sacrificial layer; exposing the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first sacrificial layer to UV light to form a second sacrificial layer having a planarized upper surface; and developing the second sacrificial layer.
- The exposing of the negative photoresist composition applied to the substrate may include exposing the negative photoresist composition to UV light using a first photomask having a passage forming layer pattern to form the first crosslinked polymer.
- The exposing of the positive photoresist composition applied to the substrate and the first crosslinked polymer may include exposing the positive photoresist composition to UV light using a second photomask having an ink chamber pattern to form the first sacrificial layer.
- The exposing of the positive photoresist composition applied to the substrate, the first crosslinked polymer, and the first sacrificial layer may include exposing the positive photoresist composition to UV light using a second photomask having an ink chamber pattern to form the second sacrificial layer having a planarized upper surface.
- The method may further include repeatedly blank exposing the second sacrificial layer having the planarized upper surface until a height of the second sacrificial layer is substantially equal to a height of the passage forming layer; developing the blank exposed second sacrificial layer; applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the substrate and the second sacrificial layer; exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to UV light to form a second crosslinked polymer; and developing the second crosslinked polymer.
- The exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer may include exposing the negative photoresist composition to UV light using a third photomask having a nozzle layer pattern to form the second crosslinked polymer.
- The method may further include applying a negative photoresist composition including a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone to the substrate and the second sacrificial layer; exposing the negative photoresist composition applied to the substrate and the second sacrificial layer to UV light to form a second crosslinked polymer; and developing the second crosslinked polymer, wherein the positive photoresist composition is an imide-based positive photoresist composition.
- The exposing of the negative photoresist composition applied to the substrate and the second sacrificial layer can include exposing the negative photoresist composition to UV light using a third photomask having a nozzle layer pattern to form the second crosslinked polymer.
- The present general inventive concept also provides an inkjet printhead including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a nozzle layer, disposed on the passage forming layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- A height of the ink chamber can be substantially equal to a height of the passage forming layer. A height of the ink chamber can be greater than a height of the passage forming layer. The passage forming layer can include a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The present general inventive concept also provides an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; and a first polymer layer, disposed on the substrate, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The present general inventive concept also provides an inkjet printhead intermediate useable to make an inkjet printhead, including: a substrate having thereon at least one heater and at least one electrode and having an ink passage; a passage forming layer, disposed on the substrate, defining an ink chamber; and a sacrificial layer having a planarized upper surface disposed on a portion of the substrate substantially surrounded by the passage forming layer.
- The passage forming layer may include a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The sacrificial layer may include an imide-based positive photoresist composition. A height of the sacrificial layer may be substantially equal to a height of the passage forming layer. A height of the sacrificial layer may be greater than a height of the passage forming layer.
- The inkjet printhead intermediate may further include a polymer layer, disposed on the sacrificial layer, including a crosslinked product of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.
- The present general inventive concept also provides a method of manufacturing an inkjet printhead, the method including: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; coating a negative photoresist composition on the substrate having thereon the heater and the electrode and patterning the negative photoresist composition using a photolithography process to form a passage forming layer that defines an ink passage; forming a sacrificial layer on the substrate having thereon the passage forming layer so as to cover the passage forming layer; planarizing upper surfaces of the passage forming layer and the sacrificial layer using a polishing process; coating the negative photoresist composition on the passage forming layer and the sacrificial layer and patterning the negative photoresist composition using a photolithography process to form a nozzle layer having a nozzle; forming an ink feed hole in the substrate; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone
- The polishing process may be a chemical mechanical polishing (CMP) process. The substrate may be a silicon wafer.
- The formation of the passage forming layer may include forming a first photoresist layer by coating the negative photoresist composition on the entire surface of the substrate; exposing the first photoresist layer using a first photomask having an ink passage pattern; and forming the passage forming layer by developing the first photoresist layer to remove an unexposed portion of the first photoresist layer.
- The sacrificial layer may include a positive photoresist or a non-photosensitive soluble polymer. The positive photoresist may be an imide-based positive photoresist. The non-photosensitive soluble polymer may be at least one selected from the group consisting of a phenolic resin, a polyurethane resin, an epoxy resin, a polyimide resin, an acrylic resin, a polyamide resin, an urea resin, a melamine resin, and a silicone resin. Here, the term “soluble” refers to characteristics that can be dissolved in a solvent.
- In the formation of the sacrificial layer, the sacrificial layer may be formed to be higher than the passage forming layer. Here, the sacrificial layer may be formed using a spin coating process.
- In the planarization of the upper surfaces of the passage forming layer and the sacrificial layer, the upper surfaces of the passage forming layer and the sacrificial layer may be polished using a polishing process such as a chemical mechanical polishing process to reach a desired height of the ink passage.
- The formation of the nozzle layer may include forming a second photoresist layer by coating the negative photoresist composition on the passage forming layer and the sacrificial layer; exposing the second photoresist layer using a second photomask having a nozzle pattern; and forming the nozzle layer having the nozzle by developing the second photoresist layer to remove an unexposed portion of the second photoresist layer.
- The formation of the ink feed hole may include coating a photoresist on a rear surface of the substrate; forming an etch mask for forming the ink feed hole by patterning the photoresist; and etching a rear surface portion of the substrate exposed through the etch mask to form the ink feed hole. Here, the rear surface of the substrate may be etched by a dry etching process using plasma or a wet etching process using tetramethylammonium hydroxide (TMAH) or KOH as an etchant.
- The negative photoresist composition may further include a cationic photoinitiator and a solvent, in addition to the prepolymer having the glycidyl ether functional group. The prepolymer having the glycidyl ether functional group may be prepared from a backbone monomer unit selected from the group consisting of phenol, o-cresol, p-cresol, bisphenol-A, an alicyclic-based compound, and mixtures thereof.
- The prepolymer having the glycidyl ether functional group may include at least one represented by Formulas 1-7 above. The prepolymer may also be addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)-1-butanol (which are commercially available under the trade name of EHPH-3150).
- The prepolymer having the glycidyl ether functional group in the negative photoresist composition may be crosslinked by exposure to radiation of actinic ray, e.g., UV light.
- The cationic photoinitiator may be a sulfonium salt or an iodonium salt.
-
- According to the present invention, an upper surface of a sacrificial layer can be planarized, and thus, it is possible to easily control the shape and dimension of an ink passage, thereby improving uniformity of the ink passage. A crosslinked polymer constituting a chamber and a nozzle layer according to the present invention is prepared by crosslinking of a prepolymer that has a plurality of glycidyl ether functional groups and a phenolic novolak resin-based backbone, a bisphenol-A backbone, or an alicyclic-based backbone. Generally, the glycidyl ether functional groups can be disposed on hydrogen positions of phenolic hydroxy groups.
-
- wherein m is an integer ranging from 1 to 25, preferably an integer of 1 to 20.
- The difunctional epoxy resin having two glycidyl ether groups can form a film with a low crosslinking density.
- The content of the difunctional epoxy resin may range from about 5 to about 50% by weight, preferably from about 10 to about 20% by weight, based on the total weight of the negative photoresist composition.
- Examples of the difunctional epoxy resin having two glycidyl ether groups include, but are not limited to, EPON 828, EPON 1004, EPON 1001F, and EPON 1010 (which are commercially obtainable from Shell Chemicals), DER-332, DER-331, and DER-164 (which are commercially obtainable from Dow Chemical Company), and ERL-4201 and ERL-4289 (which are commercially obtainable from Union Carbide Corporation).
- A multifunctional epoxy resin having more than two glycidyl ether groups will now be described.
- The multifunctional epoxy resin having more than two glycidyl ether group can form a film with a high crosslinking density, increasing a resolution and thereby preventing swelling with respect to ink or a solvent. The content of the multifunctional epoxy resin may range from about 0.5 to about 20% by weight, preferably from about 1 to about 5% by weight, based on the total weight of the negative photoresist composition.
- Examples of the multifunctional epoxy resin having more than two glycidyl ether groups include, but are not limited to, EPON SU-8 and EPON DPS-164 (which are commercially obtainable from Shell Chemicals), DEN-431 and DEN-439 (which are commercially obtainable from Dow Chemical Company), and EHPE-3150 (which is commercially obtainable from Daicel Chemical Industries, Ltd.).
- Examples of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone include compounds represented by
Formula 1 below:
The prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone may also use o-cresol or p-cresol instead of phenol when designing a backbone structure, as represented by Formulas 2 and 3 below: -
- The number n of the monomer repeating units can range from 1 to about 20, preferably from 1 to about 10.
- Examples of a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and an alicyclic-based backbone include addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)1-butanol (which are commercially available under the trade name of EHPH-3150).
- Photoinitiators are compounds that can generate ions or free radicals that initiate polymerization upon exposure to light. The content of the photoinitiator may range from about 1.0 to about 10% by weight, preferably from about 1.5 to 5% by weight, based on the total weight of the negative photoresist composition. If the content of the photoinitiator is less than 1.0% by weight, unreacted prepolymers may be left due to insufficient photopolymerization. On the other hand, if the content of the photoinitiator exceeds 10% by weight, energy higher than the energy value corresponding to a film thickness may be needed, and the wall profile of a pattern may be changed.
- Examples of suitable photoinitiators include, but are not limited to, aromatic halominum salts and aromatic onium salts of Group VA or VI elements. For example, suitable photoinitiators include, but are not limited to, UVI-6974 (which is commercially obtainable from Union Carbide Corporation), SP-172 (which is commercially obtainable from Asahi denka, Co., Ltd.), and on the like.
- Specific examples of the aromatic sulfonium salt include, but are not limited to, triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate (UVI-6974), phenylmethylbenzylsulfonium hexafluoroantimonate, phenylmethylbenzylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, methyl diphenylsulfonium tetrafluoroborate, and dimethyl phenylsulfonium hexafluorophsophate.
- Specific examples of the aromatic iodonium salt include, but are not limited to, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoroantimonate, and butylphenyl iodonium hexafluoroantimonate (SP-172).
- Examples of suitable solvents include, but are not limited to, -butyrolactone, propylene glycol methyl ether acetate (PGMEA), tetrahydrofuran (THF), methyl ethyl ketone, methy isobutyl ketone, and mixtures thereof. A suitable content of the solvent can range from about 20 to about 90% by weight, preferably from about 45 to 75% by weight, based on the total weight of the negative photoresist composition.
- As additional additives, photosensitizers, silane coupling agents, fillers, viscosity modifiers, and the like, can be used.
- Sensitizers absorb light energy and facilitate the transfer of energy to another compound, which can then form radical or ionic initiators. Sensitizers frequently expand a useful energy wavelength range for photoexposure, and typically are aromatic light absorbing chromophores. Sensitizers can also lead to the formation of photoinitiators, which can be free radical or ionic forms.
- When present, the sensitizer can be present in an amount of from about 0.1 to about 20% by weight based on the total weight of the negative photoresist composition.
-
FIGS. 3A through 3R are cross-sectional views illustrating a method of manufacturing an inkjet printhead using a prepolymer that has a glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol-A-based backbone, or an alicyclic-based backbone according to an embodiment of the present general inventive concept. - As illustrated in
FIG. 3A , aheater 141 to heat ink and anelectrode 142 to supply current to theheater 141 can be formed on asubstrate 110. - A silicon wafer is used as the
substrate 110 inFIGS. 3A-3R . A silicon wafer is widely used in manufacturing semiconductor devices and is advantageous for mass production. However, the present general inventive concept is not limited to thesubstrate 110 being a silicon wafer. - The
heater 141 can be formed by depositing a resistive heating element, such as tantalum-nitride or a tantalum-aluminum alloy, on thesubstrate 110 by sputtering or chemical vapor deposition (CVD) and patterning the deposited resistive heating element. Theelectrode 142 can be formed by depositing a metal having good conductivity, such as aluminum or an aluminum alloy, on thesubstrate 110 by sputtering and patterning the deposited metal. Although not illustrated, a passivation layer made of, for example, silicon oxide or silicon nitride, may be formed on theheater 141 and theelectrode 142. - As illustrated in
FIG. 3B , a firstnegative photoresist layer 121 can be formed on thesubstrate 110 where theheater 141 and theelectrode 142 are formed. The firstnegative photoresist layer 121 forms a passage forming layer (see 120 ofFIG. 3D ) surrounding an ink chamber and a restrictor, which will be described later. In particular, the firstnegative photoresist layer 121 can be formed by applying a negative photoresist composition containing a prepolymer having a glycidyl ether functional group to a predetermined thickness to an entire surface of thesubstrate 110. The negative photoresist composition is as described above. Here, the negative photoresist composition may be applied to a thickness substantially corresponding to a height of the ink chamber so as to accommodate the quantity of ink droplets ejected. The negative photoresist composition may be applied to thesubstrate 110 using a spin coating process. - As illustrated in
FIG. 3C , the firstnegative photoresist layer 121 can be exposed to an actinic radiation, such as UV light, using afirst photomask 161 having a passage forming layer pattern. Specifically, an exposed portion of the firstnegative photoresist layer 121 can be cured so as to have chemical resistance and high mechanical strength. On the other hand, an unexposed portion of the firstnegative photoresist layer 121 is easily dissolved in a developer. - Then, when the first
negative photoresist layer 121 is developed, the unexposed portion is removed to form a space, and the exposed and cured portion is left to form apassage forming layer 120, as illustrated inFIG. 3D . -
FIGS. 3E through 3L illustrate the formation of a sacrificial layer S in the space surrounded by thepassage forming layer 120. The sacrificial layer S has a planarized upper surface (i.e., the upper surface does not protrude at its peripheral edges, and does not bulge upward around the passage forming layer 120). According to various embodiments of the present general inventive concept, the upper surface of the sacrifical layer S can be planarized by applying a positive photoresist, patterning the positive photoresist at least twice, and planarizing the resulting structure once. - In more detail, as illustrated in
FIG. 3E , the positive photoresist can be applied to the entire surface of thesubstrate 110 having thereon thepassage forming layer 120 to a predetermined thickness by spin-coating, thereby forming a firstsacrificial layer 123. Here, the positive photoresist bulges upward due to the protrudingpassage forming layer 120, making the upper surface of the firstsacrificial layer 123 uneven. As illustrated inFIG. 3F , the firstsacrificial layer 123 can be exposed to UV light using asecond photomask 162 having a predetermined pattern covering a region between patterns of thepassage forming layer 120. Specifically, a portion of the firstsacrificial layer 123 exposed to UV light becomes easily dissolved in a developer. Thus, when the firstsacrificial layer 123 is developed, only an unexposed portion of the firstsacrificial layer 123 is left while the exposed portion is removed, as illustrated inFIG. 3G . - As illustrated in
FIG. 3H , a positive photoresist is applied for a second time to the entire surface of thesubstrate 110 having thereon thepassage forming layer 120 and the firstsacrificial layer 123 to a predetermined thickness by spin-coating, thereby forming a secondsacrificial layer 124. The upper surface of the secondsacrificial layer 124 can be planarized by the firstsacrificial layer 123 filled in the space surrounded by thepassage forming layer 120. - As illustrated in
FIG. 3I , the secondsacrificial layer 124 can be exposed to UV light using asecond photomask 162, which is identical to thefirst photomask 162 used to expose the firstsacrificial layer 123. Subsequently, the secondsacrificial layer 124 can be developed to remove an exposed portion of the secondsacrificial layer 124. As a result, as illustrated inFIG. 3J , the sacrificial layer S consisting of the firstsacrificial layer 123 and the secondsacrificial layer 124 and having the planarized upper surface can be formed in a space surrounded by thepassage forming layer 120. - As illustrated in
FIG. 3K , the sacrificial layer S can be exposed to UV light. Here, the exposing may be performed by blank exposure without using a photomask. The sacrificial layer S can be continuously exposed so that the upper surface of the sacrificial layer S becomes substantially the same height as that of thepassage forming layer 120 by controlling an exposure time and light intensity. Next, the sacrificial layer S can be developed to remove the exposed portion of the sacrificial layer S and to lower the height of the sacrificial layer S, so that the sacrificial layer S has substantially the same height as thepassage forming layer 120, as illustrated inFIG. 3L . - While the foregoing description has described that the sacrificial layer S can be formed by applying, exposing, and developing the first sacrificial layer 123 (see
FIGS. 3E-3G ), applying, exposing, and developing the second sacrificial layer 124 (seeFIGS. 3H-3J ), and then performing blank exposure and development (seeFIGS. 3K-3L ), the sacrificial layer S may be formed differently from the above-described formation. For example, after applying, exposing, and developing the first sacrificial layer 123 (seeFIGS. 3E-3G ), the application of the secondsacrificial layer 124 may be followed by performing blank exposure (as opposed to the exposure through thesecond photomask 162 illustrated inFIG. 3I ). Subsequently, development can be performed to allow the secondsacrificial layer 124 and the firstsacrificial layer 123 to remain as high as thepassage forming layer 120. Next, the same exposure using thesecond photomask 162 and development steps can be performed, leaving only the sacrificial layer S surrounded by thepassage forming layer 120. - Alternatively, the sacrificial layer S may be formed as described below. After applying, exposing, and developing the first sacrificial layer 123 (see
FIGS. 3E-3G ), the secondsacrificial layer 124 can be applied and exposed using thesecond photomask 162 and using blank exposure. Here, the sequence of exposing using thesecond photomask 162 and using blank exposure may be reversed. That is, the applied secondsacrificial layer 124 can be exposed using blank exposure followed by exposure using thesecond photomask 162. Subsequently, the exposed portion is removed by development, so that only the sacrificial layer S surrounded by thepassage forming layer 120 remains. - While the foregoing description has described that the positive photoresist is applied twice in order to form a sacrificial layer S having a planarized upper surface, the positive photoresist may be applied three or more times until the sacrificial layer S has a desired thickness. In this case, the number of times of performing exposure and development increases according to the number of times of applying positive photoresist.
- Next, as illustrated in
FIG. 3M , a secondnegative photoresist layer 131 can be formed on thesubstrate 110 where thepassage forming layer 120 and the sacrificial layer S are formed. Since the secondnegative photoresist layer 131 forms a nozzle layer (see 130FIG. 3O ), which will be described later, the secondnegative photoresist layer 131 can be formed of a material that is chemically stable against ink, like thepassage forming layer 120. For this, the secondnegative photoresist layer 131 can be formed by applying a composition containing a prepolymer having a glycidyl ether functional group to an entire surface of thesubstrate 110 to a predetermined thickness by spin coating. Here, the composition containing the prepolymer having the glycidyl ether functional group may be applied to a thickness enough to obtain a sufficiently long nozzle and to withstand a change in the pressure of the ink chamber upon formation of the secondnegative photoresist layer 131. - Since the sacrificial layer S is formed to have substantially the same height as the
passage forming layer 120, that is, the upper surface of the sacrificial layer S is planarized, it is possible to overcome the deformation or melting problem that occurs in the prior art, as discussed above. In particular, the deformation or melting of edges of the sacrificial layer S due to a reaction between the positive photoresist forming the sacrificial layer S and the material forming the secondnegative photoresist layer 131 that occurs in the prior art is avoided. Thus, the secondnegative photoresist layer 131 can be suitably adhered to thepassage forming layer 120. - As illustrated in
FIG. 3N , the secondnegative photoresist layer 131 is exposed using athird photomask 163 having a nozzle pattern. Subsequently, when the secondnegative photoresist layer 131 is developed, the unexposed portion is removed to form anozzle 154, and the exposed and cured portion is left to form anozzle layer 130, as illustrated inFIG. 3O . Actinic radiation can be used to expose the secondnegative photoresist layer 131. Specifically, a UV beam of not longer than an I-line radiation (353 nm), H-line radiation (405 nm), and G-line radiation (436 nm), or an e-beam or X-ray having wavelengths shorter than an I-line radiation can be used. - As described above, exposing by using light having a relatively short wavelength shortens a transmission length of light, so that the sacrificial layer S disposed under the second
negative photoresist layer 131 is not affected by exposure. Thus, nitrogen gas is not generated in the sacrificial layer S formed of the positive photoresist, thereby avoiding deformation of thenozzle layer 130 due to nitrogen gas. - As illustrated in
FIG. 3P , anetch mask 171 to form an ink supply hole 151 (seeFIG. 3Q ) can be formed on a rear surface of thesubstrate 110. Theetch mask 171 is formed by applying a positive or negative photoresist to the rear surface of thesubstrate 110 and patterning the same. - Next, as illustrated in
FIG. 3Q , thesubstrate 110 exposed by theetch mask 171 can be etched from the rear surface thereof to be perforated, thereby forming anink supply hole 151, followed by removing theetch mask 171. More specifically, the etching of the rear surface of thesubstrate 110 may be performed by dry etching using, for example, plasma. Alternatively, the rear surface of thesubstrate 110 may be etched by wet etching using, for example, tetramethylammonium hydroxide (TMAH) or KOH as an etchant. - Finally, the sacrificial layer S can be removed using a solvent, thereby forming an
ink chamber 153 and a restrictor 152 surrounded by thepassage forming layer 120 in a space without the sacrificial layer S, as illustrated inFIG. 3R . - In such a manner, an inkjet printhead having the structure illustrated in
FIG. 3R is completed. In embodiments, a step difference between theink chamber 153 of the inkjet printhead and the sacrificial layer S is not greater than 3 μm. -
FIGS. 4A through 4F are cross-sectional views illustrating a method of manufacturing an inkjet printhead according to another embodiment of the present general inventive concept. In the following description, the same portions as those described above with respect to the embodiment illustrated inFIGS. 3A-3N will be briefly described or omitted for the sake of brevity. - A sacrificial layer S is formed on a
substrate 210 in substantially the same manner as illustrated inFIGS. 3A through 3J , which will now be described briefly. As illustrated inFIG. 4A , thesubstrate 210 is prepared and aheater 241 to heat ink and anelectrode 242 to supply current to theheater 241 are formed on thesubstrate 210. Next, a negative photoresist composition containing a prepolymer having a glycidyl ether functional group is applied to thesubstrate 210 having thereon theheater 241 and theelectrode 242 to a predetermined thickness, followed by exposing and developing the negative photoresist composition, thereby forming apassage forming layer 220 which is a first negative photoresist layer. At this time, thepassage forming layer 220 may be formed to be slightly lower than an ink chamber having a desired height. Then, a positive photoresist composition is applied to an entire surface of thesubstrate 210 having thereon thepassage forming layer 220 to a predetermined thickness by spin-coating, thereby forming a firstsacrificial layer 223, and the applied positive photoresist composition is exposed and developed. Subsequently, the positive photoresist composition is applied a second time to the entire surface of thesubstrate 210 to a predetermined thickness by spin-coating, thereby forming a secondsacrificial layer 224, and the twice applied positive photoresist composition is exposed and developed. In such a manner, the sacrificial layer S having the first and secondsacrificial layers passage forming layer 220, as illustrated inFIG. 4A . - When forming the sacrificial layer S, an imide-based positive photoresist can be used as the positive photoresist, and blank exposure and development therefore do not need to be performed. In other words, if the imide-based positive photoresist is used as the positive photoresist, the height of the sacrificial layer S does not need to be made substantially equal to that of the
passage forming layer 220. The imide-based positive photoresist should be subjected to hard baking at approximately 140° C. after being developed. However, the imide-based positive photoresist is not affected by a solvent contained in the negative photoresist composition and does not result in the generation of nitrogen gas even upon exposure, which will be described later in more detail. - As illustrated in
FIG. 4B , a secondnegative photoresist layer 231 is formed on thesubstrate 210 having thereon thepassage forming layer 220 and the sacrificial layer S. Since the secondnegative photoresist layer 231 forms a nozzle layer (see 230 ofFIG. 4D ), which will be described later, the secondnegative photoresist layer 231 should be chemically stable against ink. For this, the secondnegative photoresist layer 231 is formed to a predetermined thickness on the entire surface of thesubstrate 210 by a spin-coating process using a composition containing a prepolymer having a glycidyl ether functional group as described above. The secondnegative photoresist layer 231 can be formed as described above for the secondnegative photoresist layer 131. - As illustrated in
FIGS. 4A and 4B , the sacrificial layer S can be formed to protrude higher than thepassage forming layer 220. However, since the sacrificial layer S is formed of the imide-based positive photoresist, it is not affected by a solvent contained in the secondnegative photoresist layer 231, as described above. Thus, unlike in the prior art, the deformation or melting problem occurring at edges of the sacrificial layer S can be avoided. - Next, as illustrated in
FIG. 4C , the secondnegative photoresist layer 231 can be exposed using aphotomask 263 having a nozzle pattern. Subsequently, when the secondnegative photoresist layer 231 is developed, an unexposed portion of the secondnegative photoresist layer 231 is removed to form anozzle 254, while the exposed and cured portion is left to form anozzle layer 230, as illustrated inFIG. 4D . - Since the imide-based positive photoresist forming the sacrificial layer S does not produce nitrogen gas even upon exposure, the deformation problem of the
nozzle layer 230 due to nitrogen gas in the prior art does not occur. Thus, radiation of an actinic ray can be used to expose the secondnegative photoresist layer 231. Specifically, a UV beam over a broadband, including I-line radiation (353 nm), H-line radiation (405 nm), and G-line radiation (436 nm), or e-beam or X-ray having wavelengths shorter than the broadband radiations, may be used. - As illustrated in
FIG. 4E , anetch mask 271 can be formed on a rear surface of thesubstrate 210, and thesubstrate 210 exposed by theetch mask 271 is etched from the rear surface thereof to be perforated by dry etching or wet etching, thereby forming anink supply hole 251. Specific steps for forming theetch mask 271 and theink supply hole 251 are the same as those illustrated inFIGS. 3P-3Q . - Finally, the sacrificial layer S can be removed using a solvent, thereby forming an
ink chamber 253 and a restrictor 252 surrounded by thepassage forming layer 220 in a space obtained by the removal of the sacrificial layer S, as illustrated inFIG. 4F . - In such a manner, an inkjet printhead having the structure illustrated in
FIG. 4F is completed. In embodiments, a step difference between the chamber layer of the inkjet printhead and the sacrificial layer is not greater than 3 μm. -
FIGS. 6A through 6L are sectional views illustrating a method of manufacturing an inkjet printhead, including forming a passage forming layer and a nozzle layer using a negative photoresist composition including a prepolymer as described above and planarizing a sacrificial layer using a chemical mechanical polishing (CMP) process. - First, as illustrated in
FIG. 6A , aheater 341 for heating ink and anelectrode 342 for supplying current to theheater 341 are formed on asubstrate 310. Here, a silicon wafer may be used as thesubstrate 310. The silicon wafer is widely used to manufacture semiconductor devices and is effective for mass production. - The
heater 341 can be formed by depositing a resistive heating element, such as tantalum-nitride or a tantalum-aluminum alloy, on thesubstrate 310 by sputtering or chemical vapor deposition (CVD) and patterning the deposited resistive heating element. Theelectrode 342 can be formed by depositing a metal having good conductivity, such as aluminum or an aluminum alloy, on thesubstrate 310 by sputtering and patterning the deposited metal. Although not illustrated, a passivation layer made of silicon oxide or silicon nitride may be formed on theheater 341 and theelectrode 342. - Next, as illustrated in
FIG. 6B , a firstnegative photoresist layer 321 is formed on thesubstrate 310 having thereon theheater 341 and theelectrode 342. The firstnegative photoresist layer 321 becomes a passage forming layer (see 320 ofFIG. 6D ) defining an ink passage including an ink chamber and a restrictor in a subsequent step as will be described later. The firstnegative photoresist layer 321 is crosslinked by radiation of actinic ray, such as UV light, and thus, is chemically stabilized against ink. The firstnegative photoresist layer 321 may be made of a composition containing a prepolymer having a glycidyl ether functional group on monomer repeating units as described above. In detail, the firstnegative photoresist layer 321 is formed by coating the composition to a predetermined thickness on the entire surface of thesubstrate 310. Here, the composition may be coated on the substrate using a spin coating process. - Next, as illustrated in
FIG. 6C , the firstnegative photoresist layer 321 is exposed to UV light using a first photomask 361 having ink chamber and restrictor patterns. In the exposure step, a portion of the firstnegative photoresist layer 321 exposed to UV light is cured and thus develops a chemical resistance and a high mechanical strength. On the other hand, an unexposed portion of the firstnegative photoresist layer 321 is easily dissolved in a developer. - Next, when the first
negative photoresist layer 321 is developed to remove the unexposed portion, as illustrated inFIG. 6D , apassage forming layer 320 defining an ink passage is formed. - Next, as illustrated in
FIG. 6E , a sacrificial layer S is formed on thesubstrate 310 so as to cover thepassage forming layer 320. Here, the sacrificial layer S is formed to have a higher height than thepassage forming layer 320. The sacrificial layer S may be formed by coating a positive photoresist or a non-photosensitive soluble polymer to a predetermined thickness on thesubstrate 310 using a spin coating process. Here, the positive photoresist may be an imide-based positive photoresist. When the sacrificial layer S is made of an imide-based positive photoresist, it is hardly affected by a solvent, and does not generate a nitrogen gas upon exposure to light. Therefore, a process of hard baking the imide-based positive photoresist at a temperature of about 140° C. is required. Meanwhile, the sacrificial layer S may also be formed by coating a liquid non-photosensitive soluble polymer to a predetermined thickness on thesubstrate 310 using a spin coating process and baking the soluble polymer. Here, the soluble polymer may be at least one selected from the group consisting of a phenolic resin, a polyurethane resin, an epoxy resin, a polyimide resin, an acrylic resin, a polyamide resin, an urea resin, a melamine resin, and a silicon resin. - Next, as illustrated in
FIG. 6F , upper surfaces of thepassage forming layer 320 and the sacrificial layer S are planarized using a CMP process. In detail, when the upper surfaces of the sacrificial layer S and thepassage forming layer 320 are polished by a CMP process to reach a desired height for the ink passage, the upper surfaces of thepassage forming layer 320 and the sacrificial layer 160 are formed at substantially the same height. - Next, as illustrate in
FIG. 6G a secondnegative photoresist layer 331 is formed on thepassage forming layer 320 and the sacrificial layer S that have been planarized. The secondnegative photoresist layer 331 may be formed using a composition containing a prepolymer having a glycidyl ether functional group on monomer repeating units as described above, like the firstnegative photoresist layer 321. The secondnegative photoresist layer 331 becomes a nozzle layer (see 330 ofFIG. 6I ) in a subsequent process as will be described later. The secondnegative photoresist layer 331 is crosslinked by radiation of actinic ray, such as UV light, and thus, is chemically stabilized against ink. Specifically, the secondnegative photoresist layer 331 is formed by coating the composition to a predetermined thickness on thepassage forming layer 320 and the sacrificial layer S using a spin coating process. Here, the secondnegative photoresist layer 331 is coated to have a thickness such that a sufficient nozzle length can be ensured and pressure variations in an ink chamber can be endured. - Moreover, since the sacrificial layer S and the
passage forming layer 320 are planarized to have the same heights, transformation or melting of an edge portion of the sacrificial layer S, which may be caused due to reaction between the material forming the secondnegative photoresist layer 331 and the material forming the sacrificial layer S, does not occur. Therefore, thesecond photoresist layer 331 can be closely adhered to the upper surface of thepassage forming layer 320. - Next, as illustrated in
FIG. 6H , the secondnegative photoresist layer 331 is exposed using asecond photomask 363 having a nozzle pattern. Then, when the secondnegative photoresist layer 331 is developed, an unexposed portion of the secondnegative photoresist layer 331 is removed to form anozzle 354, and an exposed and cured portion of the secondnegative photoresist layer 331 is left to form anozzle layer 330, as illustrated inFIG. 6I . Here, since the sacrificial layer S is made of an imide-based positive photoresist as described above, a nitrogen gas is not generated even though exposure-light reaches the sacrificial layer S beyond the secondnegative photoresist layer 331. Therefore, deformation of thenozzle layer 330 due to a nitrogen gas can be prevented. - Next, as illustrated in
FIG. 6J , anetch mask 371 for forming an ink feed hole (see 351 ofFIG. 6K ) is formed on a rear surface of thesubstrate 310. Theetch mask 371 may be formed by coating a positive or negative photoresist on the rear surface of thesubstrate 310 and patterning the photoresist. - Next, as illustrated in
FIG. 6K , a rear surface of thesubstrate 310 exposed through theetch mask 371 is etched so as to penetrate thesubstrate 310 to thereby form anink feed hole 351. Then, theetch mask 371 is removed. The etching of the rear surface of thesubstrate 310 may be performed by a dry etching process using plasma. Alternatively, the etching of the rear surface of thesubstrate 310 may also be performed by a wet etching process using tetramethylammonium hydroxide (TMAH) or KOH as an etchant. - Finally, when the sacrificial layer S is removed using a solvent, an
ink chamber 353 and a restrictor 352 surrounded by thepassage forming layer 320 are formed, and theelectrode 342 for supplying current to theheater 341 is exposed, as illustrated inFIG. 6L . This completes an inkjet printhead having the structure illustrated inFIG. 6L . - Preparation of Resist
Composition 1 - 50 ml xylene (commercially available from Samchun Chemical Co.) and 10 ml SP-172 (commercially available from Asashi Denka Korea Chemical Co.) were added to a reactor. 90 g of an epoxy resin in the trade name of EHPH-3150 (commercially available from Daicel Chemical Industries. Ltd.) was then added to the reactor, and the resultant solution was stirred for 24 hours.
- Preparation of Resist Composition 2
- A commercial resist solution of EPON SU-8 was obtained from MicroChem. Corp., and was used as received. The commercial solution included -butyrolactone contained in an amount between 25 and 50% by weight, and a mixture of triarylsulfonium hexafluoroantimonate and p-thiophenoxyphenyldiphenysulfonium hexafluoroantimonate in propylene carbonate contained in an amount between 1 and 5% by weight.
- A tantalum nitride heater pattern and an electrode pattern made of AlSiCu alloy (the content of each of Si and Cu was 1% by weight or less) were each formed to a thickness of about 500 Å on a 6-inch silicon wafer using a sputtering process and a photolithography process commonly known in the art (see
FIG. 3A ). - Next, as illustrated in
FIG. 3B , the resistcomposition 1 was spin-coated on the entire surface of the silicon wafer having thereon the heater pattern and the electrode pattern at a speed of 2000 rpm for 40 seconds and baked at 95° C. for seven minutes to form a first negative photoresist layer with a thickness of about 10 μm. Then, as illustrated inFIG. 3C , the first negative photoresist layer was exposed to UV light of I-line using a first photomask having predetermined ink chamber and restrictor patterns. At this time, the exposure dose was adjusted to 130 mJ/cm2. Then, the wafer was baked at 95° C. for three minutes, dipped in a PGMEA developer for one minute for development, and rinsed with isopropanol for 20 seconds, to complete a passage forming layer pattern (see 120 ofFIG. 3D ). - An imide-based positive photoresist (trade name: PW-1270, manufactured by TORAY) was spin-coated on the entire surface of the wafer having thereon the passage forming layer pattern at a speed of 1000 rpm for 40 seconds, and baked at about 140° C. for 10 minutes to form a first sacrificial layer (see 123 of
FIG. 3E ). The thickness of the first sacrificial layer was adjusted such that the overcoat thickness of the first sacrificial layer on the passage forming layer pattern was about 5 μm. - The first sacrificial layer was exposed to UV light of I-line using a second photomask having predetermined pattern covering region between the passage forming layer pattern. At this time, the exposure dose was adjusted to 130 mJ/cm2. Then, the wafer was baked at 95° C. for three minutes, dipped in a developer (AZ300K, manufactured by Clariant) for one minute for development, and rinsed with isopropanol for 20 seconds. This completed first sacrificial layer (see 123 of
FIG. 3G ). - An imide-based positive photoresist was spin-coated on the entire surface of the wafer having thereon the passage forming layer pattern and the first sacrificial layer, baked, exposed to light, baked (post-exposure bake), developed, and rinsed in the same manner as in the formation of the first sacrificial layer to form second sacrificial layer (see 124 of
FIG. 3J ). As a result, as illustrated inFIG. 3J , the sacrificial layer including the first sacrificial layer and the second sacrificial layer and having planarized upper surface was formed in space surrounded by the passage forming layer pattern. - Next, the sacrificial layers were subjected to blank exposure to UV light of 1-line at an exposure dose of 260 mJ/cm2 such that the UV light reached a portion of the sacrificial layer that was the same level as the upper surface of the passage forming layer pattern. Then, the sacrificial layer was subjected to post-exposure bake, development, and rinsing to remove the exposed portion of the sacrificial layer so that the height of the sacrificial layer was equal to that of the passage forming layer pattern (see
FIG. 3I ). - A nozzle layer pattern was formed on the silicon wafer having thereon the passage forming layer pattern and the sacrificial layer using the resist
composition 1 and a third photomask having a predetermined nozzle pattern under the same conditions as the formation of the passage forming layer pattern (seeFIGS. 3N and 3O ). - As illustrated in
FIG. 3P , etch mask was formed on rear surface of the silicon wafer using a photolithography process commonly known in the art to form ink feed hole. Then, as illustrated inFIG. 3Q , the rear surface of the silicon wafer exposed through the etch mask was etched using a plasma etching process to form ink feed hole, and the etch mask was then removed. At this time, an etching power of a plasma etching apparatus was adjusted to 2000 Watt, an etching gas was a mixture gas of SF6 and O2 (mixture ratio: 10:1 by volume), and an etch rate was 3.7 μm/min. - Finally, the wafer was dipped in a methyl lactate solvent for two hours to remove the sacrificial layer, thereby forming ink chamber and restrictor surrounded by the passage forming layer pattern in space obtained by the removal of the sacrificial layer, as illustrated in
FIG. 3R . This completed inkjet printhead having a structure as illustrated inFIG. 3R . -
FIGS. 5A and 5B are vertical sectional views illustrating inkjet printhead manufactured according to the above-described method. Referring toFIGS. 5A and 5B , a cavity is not formed between apassage forming layer 120 and anozzle layer 130, which suggests that thepassage forming layer 120 and thenozzle layer 130 are firmly adhered to each other. - This Example is intended to specifically describe a method of manufacturing an inkjet printhead, including forming a passage forming layer and a nozzle layer using a negative photoresist composition including a prepolymer as described above and planarizing a sacrificial layer using a CMP process.
- A tantalum nitride heater pattern, an AlSiCu alloy electrode pattern, and a passage forming layer pattern were formed on a 6-inch silicon wafer in the same manner as in Example 1 (see
FIGS. 6A through 6D ). - Next, as illustrated in
FIG. 6E , an imide-based positive photoresist was spin-coated on the entire surface of the wafer having thereon the passage forming layer pattern at a speed of 1000 rpm for 40 seconds, and baked at about 140° C. for 10 minutes to form sacrificial layer. The thickness of the sacrificial layer was adjusted such that the overcoat thickness of the sacrificial layer on the passage forming layer pattern was about 5 μm. - Next, upper surfaces of the passage forming layer pattern and the sacrificial layer were planarized using a CMP process, as illustrated in
FIG. 6F . For this, the wafer was supplied onto a polishing pad (Model No.: JSR FP 8000, manufactured by JSR) of a polishing plate such that the sacrificial layer faced the polishing pad. Then, the wafer was pressed onto the polishing pad, under a pressure of 10−15 kPa with a backing pad, by a press head. While polishing slurries (FUJIMI Corporation, POLIPLA 103) were supplied onto the polishing pad, the press head was rotated with respect to the polishing plate. At this time, the rotation speed of each of the press head and the polishing pad was 40 rpm. The backing pad was made of a material whose Shore D hardness was 30˜70. The sacrificial layer was planarized at an etch rate of 5-7 μm/min until upper surface of the passage forming layer pattern was removed by a thickness of about 1 μm. - Images of the passage forming layer pattern and the sacrificial layer after the CMP process are shown in
FIGS. 7A and 7B . Referring toFIGS. 7A and 7B , the upper surfaces of the passage forming layer pattern and the sacrificial layer were planarized by the CMP process. - Next, formation of the nozzle layer, formation of the ink feed hole, and removal of the sacrificial layer were performed in the same manner as in Example 1 except that the resist composition 2 was used as a nozzle layer forming composition, instead of the resist
composition 1 to thereby complete inkjet printhead having a structure as illustrated inFIG. 6I . -
FIGS. 8A and 8B are vertical sectional images of inkjet printhead manufactured as described in Example 2. Referring toFIGS. 8A and 8B , anink chamber 353 and arestrictor 352 are formed to have substantially equal heights, and no cavity is generated between apassage forming layer 320 and anozzle layer 330. Also, thenozzle layer 330 is firmly adhered to an upper surface of thepassage forming layer 320. - As described above, since a upper surface of a sacrificial layer is planarized in methods of manufacturing an inkjet printhead according to various embodiments of the present general inventive concept, it is possible to overcome the deformation or melting problem occurring in the prior art, that is, it is possible to avoid the deformation or melting of edges of the sacrificial layer due to a reaction between a positive photoresist composition and a negative resist composition. Thus, a shape and dimension of an ink passage can be easily controlled, thereby improving a uniformity of the ink passage, ultimately improving ink ejection performance of the inkjet printhead. Also, since a passage forming layer and a nozzle layer are suitably adhered to each other, durability of the printhead is enhanced. Further, since nitrogen gas is not generated in the sacrificial layer during photography to form a nozzle, deformation of the nozzle layer due to nitrogen gas can be avoided. Accordingly, uniformity of the ink passage can be further enhanced.
- Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.
Claims (21)
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US11/415,198 US20060262157A1 (en) | 2005-05-12 | 2006-05-02 | Method of manufacturing inkjet printhead using crosslinked polymer |
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US20090179000A1 (en) * | 2008-01-10 | 2009-07-16 | Samsung Electronics Co., Ltd | Method of manufacturing inkjet printhead and inkjet printhead manufactured using the same |
US20090278898A1 (en) * | 2008-05-08 | 2009-11-12 | Samsung Electronics Co., Ltd. | Method of manufacturing inkjet printhead and inkjet printhead manufactured using the same |
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US10654714B2 (en) | 2007-12-27 | 2020-05-19 | Stmicroelectronics, Inc. | Heating system and method for microfluidic and micromechanical applications |
US9434166B2 (en) | 2007-12-27 | 2016-09-06 | Stmicroelectronics, Inc. | Heating system and method for microfluidic and micromechanical applications |
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US8798448B2 (en) * | 2007-12-27 | 2014-08-05 | Stmicroelectronics, Inc. | Heating system and method for microfluidic and micromechanical applications |
US20090179000A1 (en) * | 2008-01-10 | 2009-07-16 | Samsung Electronics Co., Ltd | Method of manufacturing inkjet printhead and inkjet printhead manufactured using the same |
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US8293123B2 (en) * | 2008-01-10 | 2012-10-23 | Samsung Electronics Co., Ltd. | Method of manufacturing inkjet printhead and inkjet printhead manufactured using the same |
US20090278898A1 (en) * | 2008-05-08 | 2009-11-12 | Samsung Electronics Co., Ltd. | Method of manufacturing inkjet printhead and inkjet printhead manufactured using the same |
US8083324B2 (en) * | 2008-11-03 | 2011-12-27 | Samsung Electronics Co., Ltd. | Inkjet printhead and method of manufacturing the same |
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US8277023B2 (en) * | 2008-11-27 | 2012-10-02 | Samsung Electronics Co., Ltd. | Inkjet printhead and method of manufacturing the same |
US20100128091A1 (en) * | 2008-11-27 | 2010-05-27 | Samsung Electronics Co., Ltd. | Inkjet printhead and method of manufacturing the same |
US20160136638A1 (en) * | 2013-07-24 | 2016-05-19 | Jsr Corporation | Microfluidic device, process for producing the same, and channel-forming photosensitive resin composition |
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US11776808B2 (en) * | 2020-03-17 | 2023-10-03 | Tokyo Electron Limited | Planarization of spin-on films |
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KR100612027B1 (en) | 2006-08-11 |
US20060262157A1 (en) | 2006-11-23 |
JP2006315402A (en) | 2006-11-24 |
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