US20090011557A1 - Method for manufacturing a flash memory - Google Patents
Method for manufacturing a flash memory Download PDFInfo
- Publication number
- US20090011557A1 US20090011557A1 US11/863,282 US86328207A US2009011557A1 US 20090011557 A1 US20090011557 A1 US 20090011557A1 US 86328207 A US86328207 A US 86328207A US 2009011557 A1 US2009011557 A1 US 2009011557A1
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- oxide layer
- layer
- flash memory
- sacrificial
- manufacturing
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/30—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the memory core region
Definitions
- the present invention relates to a method for manufacturing a flash memory, and more particularly, to a method for manufacturing a flash memory by using a spacer as an STI oxide spacer.
- the flash memory is widely used because of its capability of non-volatile information storage. Generally speaking, the flash memory is divided into two groups, the NOR flash memory and the NAND flash memory.
- STI shallow trench isolation
- the profile of the trench formed by the dry etching must be in a shape of an “inverted trapezoid” when the STI 120 is formed by dry etching the substrate 110 and filling with an isolation material. Accordingly, the chosen location of the floating gate 130 must be in the shape of a trapezoid and have poly-Si remained therein, which will affect the isolation as well as allocation of each individual floating gate, such as bits independence and distribution and cause confusion and error of data access, such as data storage shortage.
- the present invention provides a method for manufacturing a flash memory by taking the advantages of forming a spacer on the sidewall of the STI oxide spacer as the STI oxide spacer to amend the flawed profile of the STI oxide to solve the problem in the prior art, such as bits independence and distribution or data storage shortage.
- the method for manufacturing a flash memory of the present invention includes first providing a substrate with a sacrificial oxide layer, a sacrificial poly-Si layer, a first hard mask layer and a first trench exposing part of the substrate in sequence; filling the first trench with a first oxide layer; later removing the first hard mask layer and the sacrificial poly-Si layer to form a second trench and expose the sacrificial oxide layer; afterwards depositing a oxide layer conformally on the sacrificial oxide layer and on the first oxide layer; then removing the oxide layer on the sacrificial oxide layer and on the top of the first oxide layer, and the sacrificial oxide layer to form a spacer as an STI oxide spacer surrounding the first oxide layer to allow the spacer to engage with the substrate and to allow the second trench to have an inverted trapezoidal shape and expose the substrate; later forming a floating gate oxide on the substrate, filling the second trench with the floating gate poly-Si layer and forming a second hard mask layer on
- FIG. 1 illustrates the flawed profile of the “inverted trapezoid” trench formed by the dry etching.
- FIG. 2 to FIG. 9 illustrate the method for manufacturing the flash memory of the present invention.
- a sacrificial oxide layer, an oxide layer and a trench is formed in FIG. 2 first a sacrificial oxide layer, an oxide layer and a trench is formed in FIG. 3 the trench is filled with a first oxide layer.
- the sacrificial oxide layer and the oxide layer is removed in FIG. 4 .
- an oxide layer is conformally deposited on the sacrificial oxide layer and the oxide layer.
- a spacer as a STI oxide spacer is formed.
- FIG. 7 to FIG. 9 illustrate the method for manufacturing the flash memory of the present invention.
- a pair of spacers is formed on the sidewall of the STI oxide spacer.
- Such spacer may amend the inverted trapezoid to a trapezoid, which corrects the flawed profile of the STI oxide and solves the problem of remaining poly-Si.
- FIG. 2 to FIG. 9 illustrate the method for manufacturing the flash memory 200 of the present invention.
- a substrate 210 is provided with a sacrificial oxide layer 220 , a sacrificial poly-Si layer 221 , a first hard mask layer 222 and a first trench 223 exposing part of the substrate 210 formed on and/or defined in the substrate 210 in sequence.
- the substrate 210 is usually a semiconductor substrate, such as Si.
- the thickness of the sacrificial poly-Si layer 221 is about 1500 ⁇ -1800 ⁇ , and preferably the sacrificial poly-Si layer 221 includes undoped poly-Si.
- the first hard mask layer 222 usually includes a silicon nitride material.
- the first trench 223 may be formed by dry etching to be as deep as about 1800 ⁇ -2600 ⁇ in the substrate to define the STI.
- the profile of the first trench 223 should be in a shape of an “inverted trapezoid” due to the characteristic of the dry etching.
- the first trench 223 may be filled with a first oxide layer 240 by spin-on-glass in combination with high density plasma.
- a planarization procedure may be performed to planarize the first oxide layer 240 after the first oxide layer 240 is formed.
- the first hard mask 222 layer and the sacrificial poly-Si layer 221 are removed to form a second trench 250 designated for the floating gate and the sacrificial oxide layer 220 is exposed.
- the profile of the second trench 250 should be in a shape of a trapezoid due to the profile of the first oxide layer 240 .
- the sacrificial poly-Si layer 221 and the first hard mask layer 222 may be removed by a wet etching process.
- phosphoric acid may be used.
- the sacrificial poly-Si layer 221 may be removed by using a fluoro-containing solution or an alkaline solution.
- the fluoro-containing solution may be a buffered HF solution (BHF), and the alkaline solution may be ammonia or KOH solution.
- a oxide layer 241 is conformally deposited on the sacrificial oxide layer 220 and the first oxide layer 240 , by a low pressure chemical vapor deposition process or a plasma-enhanced chemical vapor deposition process for example, such that the oxide layer 241 has a thickness of about 200 ⁇ -300 ⁇ .
- the oxide layer 241 on the sacrificial oxide layer 220 and on the top of the first oxide layer 240 is removed to form a spacer as an STI oxide spacer 242 which surrounds the first oxide layer 240 to allow the spacer 242 to engage with the substrate 210 and to allow the second trench 250 to have an inverted trapezoidal shape. Meanwhile, a portion of the sacrificial oxide layer 220 is still remained to combine with the spacer. As the characteristic of the sacrificial oxide layer 220 is substantially the same as that of the spacer, the sacrificial oxide layer 220 may be considered as a part of the spacer. Simultaneously the substrate 210 is exposed.
- the spacer 242 also widens the base of the first oxide layer 240 . Simultaneously the sacrificial oxide layer 220 is also removed. The oxide layer 241 and the sacrificial oxide layer 220 may be removed by a dry etching method.
- the profile of the first oxide layer 240 is amended from an inverted trapezoid to a trapezoid due to the lateral compensation of the oxide layer 241 . Since the remaining poly-Si would damage bits independence and distribution or cause data storage shortage, the problem of remaining poly-Si is solved by amending profile of the first oxide layer 240 from an inverted trapezoid to a trapezoid. This step is a pre-amendment of the profile of the floating gate poly-Si layer.
- the flash memory 200 may be manufactured by the conventional method.
- a floating gate oxide layer 251 of better quality may be formed on the substrate 210 and adjacent to the STI oxide spacer 242 after the STI oxide spacer 242 is formed to replace the sacrificial oxide layer 220 which covered the substrate 210 .
- the floating gate oxide layer 251 may be formed by an atmospheric pressure (AP) furnace oxidation to have a thickness of about 70 ⁇ -100 ⁇ .
- AP atmospheric pressure
- the second trench 250 may be filled with the floating gate poly-Si layer 252 doped with N-dopant by such as in-situ implantation.
- a planarization procedure may be performed to planarize the floating gate poly-Si layer 252 .
- a second hard mask layer 260 with a thickness about 1400 ⁇ -2200 ⁇ may be formed on the top of the first oxide layer 240 and on the floating gate poly-Si layer 252 .
- the second hard mask layer 260 may be a silicon nitride layer.
- the flash memory 200 may be made by the conventional method. For example, a composite dielectric structure such as a layer of oxide-nitride-oxide (ONO) which covers the second hard mask layer 260 and the floating gate poly-Si layer 252 is formed after the second hard mask layer 260 , the first oxide layer 240 and the floating gate poly-Si layer 252 are etched. Later, the essential elements such as the control gate layer, the word lines, the interlayer dielectric layer or the source contact and the drain contact may be formed. The details will not be described.
- ONO oxide-nitride-oxide
Abstract
Description
- 1. Field of the Invention
- The present invention relates to a method for manufacturing a flash memory, and more particularly, to a method for manufacturing a flash memory by using a spacer as an STI oxide spacer.
- 2. Description of the Prior Art
- The flash memory is widely used because of its capability of non-volatile information storage. Generally speaking, the flash memory is divided into two groups, the NOR flash memory and the NAND flash memory.
- In the production of the NAND flash memory, a shallow trench isolation (STI) is usually formed by a dry etching and later the location and the shape of the poly-Si of the floating gate are defined by the STI.
- However, as shown in
FIG. 1 , the profile of the trench formed by the dry etching must be in a shape of an “inverted trapezoid” when theSTI 120 is formed by dry etching thesubstrate 110 and filling with an isolation material. Accordingly, the chosen location of thefloating gate 130 must be in the shape of a trapezoid and have poly-Si remained therein, which will affect the isolation as well as allocation of each individual floating gate, such as bits independence and distribution and cause confusion and error of data access, such as data storage shortage. - Therefore, a novel method is needed for manufacturing the flash memory, which is capable of amending the flawed profile of the STI oxide to solve the problem.
- The present invention provides a method for manufacturing a flash memory by taking the advantages of forming a spacer on the sidewall of the STI oxide spacer as the STI oxide spacer to amend the flawed profile of the STI oxide to solve the problem in the prior art, such as bits independence and distribution or data storage shortage.
- The method for manufacturing a flash memory of the present invention includes first providing a substrate with a sacrificial oxide layer, a sacrificial poly-Si layer, a first hard mask layer and a first trench exposing part of the substrate in sequence; filling the first trench with a first oxide layer; later removing the first hard mask layer and the sacrificial poly-Si layer to form a second trench and expose the sacrificial oxide layer; afterwards depositing a oxide layer conformally on the sacrificial oxide layer and on the first oxide layer; then removing the oxide layer on the sacrificial oxide layer and on the top of the first oxide layer, and the sacrificial oxide layer to form a spacer as an STI oxide spacer surrounding the first oxide layer to allow the spacer to engage with the substrate and to allow the second trench to have an inverted trapezoidal shape and expose the substrate; later forming a floating gate oxide on the substrate, filling the second trench with the floating gate poly-Si layer and forming a second hard mask layer on the top of the first oxide layer and on the floating gate poly-Si layer.
- These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
-
FIG. 1 illustrates the flawed profile of the “inverted trapezoid” trench formed by the dry etching. -
FIG. 2 toFIG. 9 illustrate the method for manufacturing the flash memory of the present invention. InFIG. 2 first a sacrificial oxide layer, an oxide layer and a trench is formed. InFIG. 3 the trench is filled with a first oxide layer. InFIG. 4 the sacrificial oxide layer and the oxide layer is removed. InFIG. 5 an oxide layer is conformally deposited on the sacrificial oxide layer and the oxide layer. InFIG. 6 a spacer as a STI oxide spacer is formed.FIG. 7 toFIG. 9 illustrate the method for manufacturing the flash memory of the present invention. - In the method for manufacturing a flash memory of the present invention after the STI oxide is formed, a pair of spacers is formed on the sidewall of the STI oxide spacer. Such spacer may amend the inverted trapezoid to a trapezoid, which corrects the flawed profile of the STI oxide and solves the problem of remaining poly-Si.
-
FIG. 2 toFIG. 9 illustrate the method for manufacturing theflash memory 200 of the present invention. First as shown inFIG. 2 , asubstrate 210 is provided with asacrificial oxide layer 220, a sacrificial poly-Si layer 221, a firsthard mask layer 222 and afirst trench 223 exposing part of thesubstrate 210 formed on and/or defined in thesubstrate 210 in sequence. - The
substrate 210 is usually a semiconductor substrate, such as Si. The thickness of the sacrificial poly-Si layer 221 is about 1500 Å-1800 Å, and preferably the sacrificial poly-Si layer 221 includes undoped poly-Si. The firsthard mask layer 222 usually includes a silicon nitride material. Thefirst trench 223 may be formed by dry etching to be as deep as about 1800 Å-2600 Å in the substrate to define the STI. The profile of thefirst trench 223 should be in a shape of an “inverted trapezoid” due to the characteristic of the dry etching. - Referring to
FIG. 3 , thefirst trench 223 may be filled with afirst oxide layer 240 by spin-on-glass in combination with high density plasma. - Optionally, a planarization procedure may be performed to planarize the
first oxide layer 240 after thefirst oxide layer 240 is formed. - Referring to
FIG. 4 as well asFIG. 3 for reference, the firsthard mask 222 layer and the sacrificial poly-Si layer 221 are removed to form asecond trench 250 designated for the floating gate and thesacrificial oxide layer 220 is exposed. The profile of thesecond trench 250 should be in a shape of a trapezoid due to the profile of thefirst oxide layer 240. - The sacrificial poly-
Si layer 221 and the firsthard mask layer 222 may be removed by a wet etching process. For example, if the firsthard mask layer 222 includes silicon nitride, phosphoric acid may be used. The sacrificial poly-Si layer 221 may be removed by using a fluoro-containing solution or an alkaline solution. The fluoro-containing solution may be a buffered HF solution (BHF), and the alkaline solution may be ammonia or KOH solution. - Referring to
FIG. 5 , aoxide layer 241 is conformally deposited on thesacrificial oxide layer 220 and thefirst oxide layer 240, by a low pressure chemical vapor deposition process or a plasma-enhanced chemical vapor deposition process for example, such that theoxide layer 241 has a thickness of about 200 Å-300 Å. - Referring to
FIG. 6 , theoxide layer 241 on thesacrificial oxide layer 220 and on the top of thefirst oxide layer 240 is removed to form a spacer as anSTI oxide spacer 242 which surrounds thefirst oxide layer 240 to allow thespacer 242 to engage with thesubstrate 210 and to allow thesecond trench 250 to have an inverted trapezoidal shape. Meanwhile, a portion of thesacrificial oxide layer 220 is still remained to combine with the spacer. As the characteristic of thesacrificial oxide layer 220 is substantially the same as that of the spacer, thesacrificial oxide layer 220 may be considered as a part of the spacer. Simultaneously thesubstrate 210 is exposed. Thespacer 242 also widens the base of thefirst oxide layer 240. Simultaneously thesacrificial oxide layer 220 is also removed. Theoxide layer 241 and thesacrificial oxide layer 220 may be removed by a dry etching method. - Now the profile of the
first oxide layer 240 is amended from an inverted trapezoid to a trapezoid due to the lateral compensation of theoxide layer 241. Since the remaining poly-Si would damage bits independence and distribution or cause data storage shortage, the problem of remaining poly-Si is solved by amending profile of thefirst oxide layer 240 from an inverted trapezoid to a trapezoid. This step is a pre-amendment of the profile of the floating gate poly-Si layer. - Referring to
FIG. 7 , now theflash memory 200 may be manufactured by the conventional method. For example, a floatinggate oxide layer 251 of better quality may be formed on thesubstrate 210 and adjacent to theSTI oxide spacer 242 after theSTI oxide spacer 242 is formed to replace thesacrificial oxide layer 220 which covered thesubstrate 210. The floatinggate oxide layer 251 may be formed by an atmospheric pressure (AP) furnace oxidation to have a thickness of about 70 Å-100 Å. - With reference to
FIG. 8 , thesecond trench 250 may be filled with the floating gate poly-Si layer 252 doped with N-dopant by such as in-situ implantation. Optionally, a planarization procedure may be performed to planarize the floating gate poly-Si layer 252. - With reference to
FIG. 9 , a secondhard mask layer 260 with a thickness about 1400 Å-2200 Å may be formed on the top of thefirst oxide layer 240 and on the floating gate poly-Si layer 252. The secondhard mask layer 260 may be a silicon nitride layer. - After the second
hard mask layer 260 is formed, theflash memory 200 may be made by the conventional method. For example, a composite dielectric structure such as a layer of oxide-nitride-oxide (ONO) which covers the secondhard mask layer 260 and the floating gate poly-Si layer 252 is formed after the secondhard mask layer 260, thefirst oxide layer 240 and the floating gate poly-Si layer 252 are etched. Later, the essential elements such as the control gate layer, the word lines, the interlayer dielectric layer or the source contact and the drain contact may be formed. The details will not be described. - Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
Claims (9)
Applications Claiming Priority (2)
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TW096124148A TWI343634B (en) | 2007-07-03 | 2007-07-03 | Method for manufacturing flash memory |
TW096124148 | 2007-07-03 |
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US20090011557A1 true US20090011557A1 (en) | 2009-01-08 |
US7482227B1 US7482227B1 (en) | 2009-01-27 |
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US11/863,282 Active 2027-10-01 US7482227B1 (en) | 2007-07-03 | 2007-09-28 | Method for manufacturing a flash memory |
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Cited By (1)
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CN105023879A (en) * | 2014-04-16 | 2015-11-04 | 华邦电子股份有限公司 | Manufacturing method of semiconductor component |
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CN102386080B (en) * | 2010-09-02 | 2014-03-12 | 中芯国际集成电路制造(上海)有限公司 | Method for forming metal gate |
Citations (6)
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US20030119256A1 (en) * | 2001-12-22 | 2003-06-26 | Dong Cha Deok | Flash memory cell and method of manufacturing the same |
US20060205151A1 (en) * | 2005-03-10 | 2006-09-14 | Hynix Semiconductor Inc. | Method of fabricating flash memory device |
US20060223263A1 (en) * | 2005-03-31 | 2006-10-05 | Hynix Semiconductor Inc. | Method of forming transistor using step STI profile in memory device |
US20070134877A1 (en) * | 2005-12-12 | 2007-06-14 | Hynix Semiconductor Inc. | Method of forming gate of flash memory device |
US20070138537A1 (en) * | 2005-12-21 | 2007-06-21 | Song Hee Park | Non-volatile memory device and method of fabricating a non-volatile memory device |
US7341913B2 (en) * | 2005-12-26 | 2008-03-11 | Powerchip Semiconductor Corp. | Method of manufacturing non-volatile memory |
-
2007
- 2007-07-03 TW TW096124148A patent/TWI343634B/en active
- 2007-09-28 US US11/863,282 patent/US7482227B1/en active Active
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20030119256A1 (en) * | 2001-12-22 | 2003-06-26 | Dong Cha Deok | Flash memory cell and method of manufacturing the same |
US20060205151A1 (en) * | 2005-03-10 | 2006-09-14 | Hynix Semiconductor Inc. | Method of fabricating flash memory device |
US20060223263A1 (en) * | 2005-03-31 | 2006-10-05 | Hynix Semiconductor Inc. | Method of forming transistor using step STI profile in memory device |
US20070134877A1 (en) * | 2005-12-12 | 2007-06-14 | Hynix Semiconductor Inc. | Method of forming gate of flash memory device |
US20070138537A1 (en) * | 2005-12-21 | 2007-06-21 | Song Hee Park | Non-volatile memory device and method of fabricating a non-volatile memory device |
US7341913B2 (en) * | 2005-12-26 | 2008-03-11 | Powerchip Semiconductor Corp. | Method of manufacturing non-volatile memory |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN105023879A (en) * | 2014-04-16 | 2015-11-04 | 华邦电子股份有限公司 | Manufacturing method of semiconductor component |
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TW200903732A (en) | 2009-01-16 |
TWI343634B (en) | 2011-06-11 |
US7482227B1 (en) | 2009-01-27 |
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