CA2120325A1 - Ultracleaning of involuted microparts - Google Patents

Abstract

A method for cleaning a component having a complex configuration utilizing a surfactant wash and sonic cavitation followed by drying with an organic solvent or vapor is disclosed. An apparatus containing an enclosure (12) for holding the object to be cleaned, means (14) for holding the object in place within the enclosure, at least one port (22) for passing treatment fluids through the enclosure, and a sonic generator (16) adjacent to the enclosure is used for carrying out the method. In a preferred embodiment, the apparatus contains a port (76) or valve (78) for allowing hot organic vapor to enter the chamber, and a means for pressurizing the enclosure to a superatmospheric pressure.

Description

W093/06949 2 1 2 ~ 3 2 ~ PC~/U~92/0~15 ULTRACLEANING OF INVOLUTED MICROPARTS

There are numerous applications for th~ ~leaning of sensitive components, such as spacecraft components bearings, and elec~ronic equipment~ Electronic or elec~rical components can become contaminated through usage, eOg., by smoke, dust, and other airborne ~ontaminants, or by oils or lubricants. Oils are more diffic~lt to displace than many other contaminants due to their lower surface tensions and higher viscositi~s, which make them difficul~ ~o remove with many sol~ents and/or detergents.
A num~er of alcohols, fluorinated alcohols and other halo~enated compounds have been found to be l~ effective as displacing agents for contaminants, ~articularly oily contaminants. For example, chlorinated hydrocarbons and c!hlorofluorocarbons (CFCs), such as FreonsT M ~ are commonly used.
Concentra~ed corrosive acids or bases have also been : 20 used as cle~ning agents. These reagents are often costly, hazardous to handle and present environmental and disposal problems.
Sonic cleaning has been used for decontaminating and/or disinfecting instruments used in medical, 2~: dentall surgical or food processing, for example. This method generally involves placing the instruments in an aqueous bath and tre}sting them with ultrasonic energy.
Treatment with ul~rasonic energy has long been ~! I ' j .
recognizgd to be lethal to microorganisms suspended in ., , . ~ , ,., .. , .. ~ , . . . . . .

Wog3/06s4s PcT/uss2~o~ls 212~32~ `

a liquid, as described, for example, by Boucher in U~S.
Patent No. 4,211,744 (1980). Ultrasonic energy has also been used for cleaning and sterilizing contact lenses (U.S. Pa~en~ 4,382,824 ~alleck (1983~)! surgical instruments (u.s. Patent 4,193,818, Young ~t al. (1980) and U.S. Patent 4,448,750 (1984)) and even body parts, such as a doctor~s hands (u.s. Patent 3,481,687, Fishman (196~)).
Af~er fluid processing, the components normally need ~c ~e dried. Evaporation of rinsing liquids is not desirable since it often leads ~o spotting or streaking. Even ~he evaporation of ultra high purity water can lead to problems when drying on the surfaces of some components. For example t such water can 1~ dissolve traces of silicon and silicon dioxide on semiconductor surfaces, and su3~sequent evaporation will leave residues of the solute material on the wafer surface.
A device known as a spin-rinser~drier is useful for 2~ drying objects withou~ water evaporation. These devices utilize centrifugal force to ~throw~' the water off the s~rfaces of the object. This can raUse ~reakage because of the mechanical stress placed on the object, particularly with larger or fragile objects.
In addi~ion, contamination control is problematic due to the mechanical complexity of the spin-rinser-drier~
Since the objects conventionally travel through dry nitrogen at a hi~h ~elscity, static electric charges can develop on the surface of the objectO Opposi~ely charged airborne particles are then quickly drawn ~o the object's surface when the drier is opened, resulting in particulate contamination. Finally, it is difficult to avoid evaporation of water from the surface of the object during the spin cycle with the attendant disadvantages discussed above.

W093/06949 PCT/US92/0~15 2~1)32~

More recen~ly, me~hods and devices have been developed for steam or chemical drying of sensiti~e objectsO Chemical drying generally comprises two steps. First, the rinsing fluid is driven off and replaced by a non-aqueous drying 1uid. S~'cond, the non-aqueous drying fluid is evaporated using a pre-dried gas, such as nitrogen. A method for chemically drying semiconductor wafers using isopropanol is described in U.S~ Patent No. 4,778 r 532, and in U.S.
Patent No. 4,911,7610 It is an object of the present invention to provide a process and apparatus which can be used for degreasing, cleaning and drying of sensitiv~
componPntS ~ particularly components having complex configurationsO

~ I I

. ~

W093/0694~ PCT/US92tO~15 212~32~ `

Summar of the Invention Y ._ _ The present invention relates to methods and apparatus for cleaning the surface of an ohject by placing the object in an enclosed vessel and sequentially passing cleaning and/or rinsi~g fluids through the vessel, then drying the objeot under conditions which do not permit the deposition of residues on the surf~ce o the object. The cl~aning and rinsing fluids are selected based on the type of contamination to be removed and can include aqueous and non aqueous flu~ds. In a preferred embodiment, sonic energy is applied to at least one of the fluids in ~he vessel.
The process is particularly useful for cleaning l~ sensi~ive electranic ~amponents, such as complex parts, e.g~, reading heads used in camputer systems for reading and/or recording information on disks. The process is useful far cleaning hard disks, aerospace parts ~e.g~, gyroscopes, ball bearings), medical de~ices and other precision parts. The process can be used to deflux printed circuit boards, and for degressing microparts, in particular, as a replacement f~r traditional FreonT M processing. Components having numerous interfaces and facets, that is, which are involu~ed, can be ~horoughly cleaned and dried using the presen~ method. The present protocols can be used on metallic, ceramic or plastic surfaces.
The apparatus comprises an enclosure for enclosing the objec~ tD be cleaned, and means for passing a flow olf 1iquid though the enclosure and around the o~ject disposed therein. Cleaning and rinsing li~uids are preferably introduced into the vessel through a port located in the bottom of the vessel. The apparatus may include a means for agitating the liquid ta permit wo93/o694s PCT/~S92/0~5 212~32~

thorough cleaning or rinsing of all surfaces.
Prefer bly a means for generating sor~ waves, which can be ultrasonic: or megasonic energy, is used for this purposa. The apparatus optionally can contai~ spray heads for pre-cleaning the object by spraylng it with a liquid to remove gross contaminants. The apparatus contains a means for removing the liquid from the enclosure which can be a second port located at the top of the vessel, and means for drying the object by filling the vessel with an organic drying solvent or vapor.
In a preferred embodiment of the invention, means or introducing inert gas or air and means for circulating the washing or rinsing liquids through the vessel are included in the appara~us. The vessel prefera~ly comprises a port at its ~op so ~hat a fluid in the vessel can be ven ed out: the top port while a : second fluid is introduced into the ve~sel through the bottom port. Vapor or gas is :in~roduced through an inlet at the top to displace a fluid d~wnwardly ~hrough ~: the bottom. This allows one ~luid to be directly ; replaced with another fluid without exposing the : objects to air. The two ports may be connected via a line, thereby permitting a fluid to be circulated 2~ ~hrough the vessel. The apparatus preferably includes mean for supplying the vessel with a washing or rinsing liquid withou~ exposing the fluid to the air.
: In ~ne embodiment~ a storage tank containin~ the liquid is connected to the vessel via a line. Th~ storage tank may be supplied with a means for pressurizing the tank, for example, with an inert gas. The washing or rin~ing liquid is then returned to the tank after use.
In another embodiment, the apparatus contains means for fil~ering, distilling or otherwise recycling ~he liquids for reuse in the present system.

W093/06949 PC~/US92/0~15 ~12032~

The method of the invention g~nerally involves the following steps: placing the object to be cleaned in the Yessel and sealing the vessel; filling the vessel wikh a washing fluid to immerse the object an~ contact all of the surfaces of the object with th~ 1uid, preferably, agitating the liquid using sonic energy or other agitating means; filling the vessel with a rinsing fluid to displace the washing fluid and to immerse the object; and removing rinsing fluid from the surfaces of the object using an organic drying solvent under condi~ions such tha~ substantially no rinsing fluid droplets, cleanin~ agents or contaminants are left on the surfaces of the object after removal of the rinsing fluid. The vessel can be purged with an inert gas, such as nitrogen, and/or with air, prior to removing the ob~ec~ from the vessel.
In one embodiment of ~he method~ the object of in~erest is oleaned using an agueous or semi-aqueous proto~ol~ In this embodiment, the object is immobilized in the en~losure andp optionally, prerinsed ~y spraying the object with water. The enclosure is then filled with rinse water to remove mechanically displaced surfaoe contaminants or gross particulates.
In the aqueous protocol, the objec~ is then immersed in 2~ a cleaning solution comprising a water/surfactant mixture, In the semi-aqueous protocol, khe cleaning liquid is preferably a hy~rocarbon solvent/surfactant mixture. Ultrasonic or megasonic energy can be applied through the liquid medium if desired or needed~ The : ! 30 resul~ing agitation allows even involuted or hard-to-reach surf aces of ~he component to be thoroughly cleaned~ The parts remain stationary while the cleaning and rinsin~ fluids move around them. The component is rinsed again with water to remove the W~93/0~94~ PCT/US92~0~15 212~32~

surfactant~ In a preferred embodiment, the final rinse is followed by a drying step in which a water-miscible organic vapor, e.g., alcohol or acetone vapor, is injected into ~he vessel. The organic vapo~ dri~es the water from all surfaces of the component. 'The vessel containiny the alcohol-dried component can then, optionally, be purged with nitrogen and/or air prior to removing it from the vessel. This ensures that all surfaces of the object are thoroughly dried and residue-free.
In another embodiment of the method, the object of interest is cleaned using a non-aqueous protocol. The object is immobilized in the enclosure and~ optionally, prerinsed with water or an organic solvent to remove gross particulates. The object is then immersed in an organic cleaning soivent, preferably a terpene or mixtuxe of terpenes. The terpene solvent optionally can contain a surfactant. Ultrasonic or megasonic energy is applied if necessary or desirable. The `: 20 cleaning solvent is then drained from the vessel, and the vessel is filled with a rinsing solvent which solubilizes residual cleaning solvent and removes it from the surfaces of the object. This rinsing s;tep can be followed by drying wi~h hot organio vapor. The 25 vessel is then purged with an inert gas which ~: thoroughly dries the object before it is exposed to air .
The method and apparatus are par~icul arly useful for ultracleaning of objects which must be as f:ree as 30 possible bf contamination. The combination of preeîse control of solvent, washing and rinsing reagents, hydraulically full flow, ul~rasonic or megasonic energization and removal of rinse droplets and/or contaminants with a drying solvent or vapor permits W~93/06949 PCr/US92/~lS
~12032~ ~ ~

extraordinarily thorough cleaning and rinsing to produce essentially contaminant-free surfaces. The ~.
results achieved through use of the apparatus and process of the invention is referred to her~eafter as "ultracleaning".
The present apparatus and method incorporates many desirable features for cleaning sensi~ive electronic components, ball bearings, printed circuit boards, medical devices, hard disks for co~puters and precision parts. The apparatus and method can be used to thoroughly clean and/or decontaminate the sltrfaces of objects containing many small par~s, involuted surfaces ur having a highly complex configuration. The reaction vessel is a totally enclosed environment, therefore 1~ contact of a human operator with aggressive cleaning solvents or solvents having a strong odor, such as ~erpenes, is eliminated. The use of terpenes is particularly advant~geous in that terpenes are naturally occurring, biodegradable, and are excellent solvents for most contaminants. Terpenes can be used for cleaning objects which traditionally required the use of Freons, which are costly and environmentally hanmful. The odor associated with mosk terpenes is not problema~ic because the system is completely enclosed.
: 25 The objects to be treated are immobilized in the ~ssel, so fragile or sensitive parts can be cleaned wi~h no product msvement. Non-aqueous sol~ents can be : recycled for repeated reuse. The apparatus and method : provides a ~ombined cleaning and drying tool, ~hereby 3~ Ireducing equipment cost, minimizing product movement and exposure to chemicals. The method eliminates harmful gas-liquid interfaces, which can result in flash corrosion and/or staining, and protects the cleaned product from sources of external contamination.

W~ 93/06g49 PCr/VS92/0841~
2121~32~

The method can be adapted f or automated chemical handllng and comprehensive computer integration of the proeess ..
. .

WO93/06g49 PCT/US92/0~15 2120~2S -`

The foreg~ing summary and objects of the invention, and the various eatures thereof, as well as the invention itself, may be more fully understood from the following description~ when read together ~ith the accompanying drawings.
Figure 1 is a schematic cross-sectional diagram illustrating an embodi~ent of the apparatus of the present invention for aqueous processing.
Figure 2 is a schema~ic cross-sectional diagram illustrating an embodiment of ~he apparatus of the present invention for aqueous processing, including drain valves for removing fluids from the vessel.
Figure 3 i5 a schema~ic diagram illustrating an 1~ embodiment of the apparatus of the p..esent invention for n~n- queous processing, inc:luding` chemical storage t~nks ~nd condui~s, valves, ancl associated equipmen~
for reuse of valuable solvents~.
:~ Figure 4 is a schematic diagram illustrating an appara~us for providing organic drying vapor to the ~ ~ vesselO
:

~' wo93/o694s P~T~U~92J0~15 212!3325 Detailed_Descri~tion of the Invention The present invention is directed to the ultracleaning of objects, particularly ob]ects having complex configurationsO The present appara~us and .
methods wîll be described herein with partgcular reference to the ultracleaning of involuted microparts, however, the general principles apply to the cleaning of other objects.
Referring to the drawings, an apparatus sui~able for caxrying out the present ultracleaning method using an aqueous protocol is shown schematically in Figure 1.
A vessel 12 holdings the object(s) for treatment with aqueous washing and rinsing fluids, and water-miscible organi~ gases and drying vapors. Vessel 12 contains disposed within its chamber means 14 for supporting or otherwise holding ~he objec~s t:o be cleaned which can be, for example/ a basket, rac}c, tray or other device.
The configura~ion of holding means 14 will depend in part upon the size~ type and configuration of the object~s) to be cleaned. Sealable ha~ch door 28 allows access to the interior of vessel 12. ~essel 12 has a tapered bottom comprising slopin~ walls to facilitate draining of cleaning and rinsing fluids from the ~essel. Yessel 12 is provided with valves 70 and 72 2~ for the control of water for rinsing and/or cleaning, which may enter and exit vessel 12 for treatment of the obje~ts.
Water is introduced via valve 70 through lines 84, 82 and inlet 22 which allows vessel 12 to be filled ! ~ 30 with the ~reatment fluid- The fluid flows upwardly through vessel 12. An inlet 74 for adding surfactant to the water is also provided. ~fter filling of vessel 12, valve 70 for controlling the water supply is closed. In a preferred embodiment, vessel 12 has at wo93/o6s4s pcT/uss2/o~1s 21~32t~ `

least one sonic transducer 16 mounted in the sides of vessel 12 for induoing ultrasonic or megasonic cavitation in a treatment fluid.
Vessel 12 optionally contains ~pray heads.26 mounted in the sides of the vessel. The s~ray heads spray water or other fluid onto the objects in the vessel to prerinse the objec~s in order to remove gross dirt and contaminants. The prerinsing fluid is conducted to spray heads 26 through conduit 86 by openin~ valve 30.
Cleaning and rinsing fluids which are used in the process can be removed from the vessel by draining through port 24 and inlet 22. Valve 72 is opened to permit the used liquid to be removed for disposal 1~ through line 82. Alternati~elyl a first fluid in vessel 12 can be displaced by i.njecting a second fluid through inlet 22 and port 24 and opening port 32, thereby forcing the first fluidl to the top of the vessel through port 32 and line~ 24. This method allows direc~ ~isplace~ent of one flui.d by ano~her without exposing the objects inside the vessel to air. Line 34 can lead to a drain, or a holding tank for the ~luid.
In another embodiment of the process, fluid can be circul ted through a loop Greated by connecting line 84 2~ with line 34~ In this aspect, shown in Figure 1, lines 34, 84 are connected by line 86. Valves 8Ei and 90 are opened to form a complete loop including vessel 12 and lines 34, 86, 84 and 82. This e~bodiment achieves purity of the trèatment fluld by providing a !~ 30 ~losed 1uid 140p in which the treatment fluid can be circulated to provide fluids at controlled flow and temperature conditions, while penmitting efficient and complete changing of the fluids in the loop. A
plurality of different fluids can be mixed and W093/06949 P~T/US92/~15 212032~

- ~3 -delivered to the loop without contaminatiny or being contaminated by any mechanical par~s o~her than the necessary valves and conduits, while efficiently conserving the fluids.
Another embodiment of the present appa~atus is shown in ~igure 2. In this embodiment, vessel 12 is provided with one or more drains 36 for removin~
cleaning and rinsing fluids from the vessel. In this aspPct, the abjects to be cleaned are placed in vessel 12 as described above. The vessel is filled with aqueous cleaning or rinsing fluid through line 82 and valve 70. The fluids are drained out through drains 36 by opening valves 380 A vessel which is approprlate for use with organic 1~ solvents is shown in Figure 3. As shown in ~igure 3, one or more storage tanks 58 r 60 for storing the cleaning, rinsin~ or drying sol.vents are connected to vessel 12 via lines 66 and 64. Each storage tank is preferably equipped with a nitrogen supply 44, 54 and exhaust 46, 56. In operationt ni~rogen is admitted to tank 58 or 60 to pressurize the contents, and Yalve 40 or 42 is opened, causing the solvent in the tank to flow into vessel 12 through inlet 62. Once the cleanin~ or rinsing cycle is complete, the solvent is 2~ drained back through line 62 and returned to the ~ank for reuse or recycling~ The apparatus can contain a gauge 68 which indiea~es the level of solvent in the ~essel.
~he apparatus contains a means for drying the objec~s using a drying solvent, which can be in liquid or vapor form. In a preferred embodiment, the drying solvent is a hot organic vapor. For this purpose, each apparatus shown in ~igures 1, 2 and 3 includes an inlet for introducing hot organic drying vapor into WO 93/0~9~9 PCI'/U~g2/~
2 1 2 0 3 2 ~

vessel 12O As shown in Figures 1, 2 ~nd 3, the organic drying vapor is introduced into vessel 12 through valves 7B and 76. The organic vapor is supplied to th ~essel :Erom a device which vaporizes the organic 5 solvent. An apparatus and process for uti~llzing drying vapor is described in UOS. Patent 4,911,761, which is incorporated herein by reference. A suitable device 12û for use in the presen~ system is shown in ~igure 4.
As shown in Figure 4, device 120 contains a bs~iler 24 for producing the organic drying vapor.
Boiler 124 contains an inlet 126 and an outlet 128, and is provided with heating bands 130 or other suitable heat ~ransfer device ~o ~uickly heat the drying fluid 15 above its boiling point. A pressuxe indicator 132 pro~rid~s information fc~r controlling the heat range, and temperature indicator 134 monitors the temperature of the fluid leaving outlet 128. ~he boiler 124 should lways ~e main~ained full of clrying fluid so that the 20 heat ~ransfer services are continually i.mmersed. For this purpose ~ a liquid level detector 135 and switch can he provided7 A safety relief valve 136 is provided at the top of boiler 12~. A ~alve 138 controls access to delivery line 122. Also connected to line 122 is a 2~ source of gas which is preferably ~ilterPd nitrogen.
Val~e 137 provides access to line 122 for the gas.
~ o effect drying of the microparts in the vessel, the pressurized oryanic vapor is introduced into vessel 12 through valves 78 and 76. It is desired to 30 dry the microparts without the formakion of ~ubbles and without leaving droplets or residual moisture on any of the surfaces of the parts, including interior surfaces.
Droplets and residual moisture may contain coIltaminant residues of the solutes. Removal of all residual wo93/o~s4s PCT/U~2/~84~5 ~12Q3~

rinsing solvent is accomplished by providing a flow of hot orga~ic vapor into the vessel in such a manner that the vapor is introduced into the top of the vessel as the rinsing fluid îs drai~ing from the bott~m, ~hrough port 24 and outlet 220 The organic vapor fs selected so that it is miscible with the rinsing liquid. In a preferred embodiment, heated isopropyl alcohol (IPA~ or acetone vapor is introduced into ~essel 12, as the rinsing fluid is displaced downward. Droplets which remain on the suraces of the microparts are carried off by the organic vapor. The IPA or acetone layer ~apor combines with the rinse liquid, which is usually wa~er or a terpene solventt to form an azeotrope layer which evaporates at a lower temperature than either the 1~ rinse liquid or the organic drying solvent. The temperature of the medium being displaced is important.
Preferably, ~he temperature is about 55 to 609C. If the temperature is mu~h higher the azeotrope layer may ~reak d~wn. Although the organic solvent and the water are miscible, ~he azeotrope layer remains distinct ~ecause of the surface ~ension and the~mal differences between the solven~ and the water. Once the rinse liquid has drained completely, ~essel 12 is purged of ~he drying vapor with a flow of clean gas, preferably nitrogen. Nitrogen is introduced into vessel 12 ~ through valves 80 and 7~. ~he azeotropic residue is : c~rri~d off in the flow of the gas. The resulting microparts are ul~raclean after this treatment, and all of the involuted surfaces are dry~
The system c~n contain spring-loaded units so that~
if the failure of the control system for the various Yalves and units should occur, treatment fluids will ~lush harmlessly out of the units to the drain, and no excessive pressure buildup will occur. Suitable ., ,,.. ., . . ,. ~ . . ~ . ~

W093/06949 P~T/U~9~/0~1~

mechanisms are those described, for example, in U.S~ Pa~en~ 4,899,767, the teachings of which are hereby incorporated herein by xeference~
The method is generally carried out acco~ding to the following procedure. The objert to b~ eaned is placed in vessel 12 having a chamber therewithin, serviced by at least one port 24. The chamber of the ~essel is preferably sealed. ~luids used for rinsing and~or cleaning the objec~ are passed into ~he vessel through port 24 until the surfaces of the object are immersed in the 1uid. Ultrasonic or megasonic energy can then be applied to at least one o the fluids in the ~essel. The rinsing liquid is drained out slowly to help maintain ~he integrity of the azeotrope layer.
The rate of descent is preferably ~ ra~e which avoids turbulence which disrupts the surface tension of the azeotrope layer and avoids lea~ing droplets, generally about 2 inches per minute or J.es~. The displace~ent step is preferably carried out: at a positive pressure ~0 of about 1 to 2 psig.
: If an a~uenus cleaning protocol is used, the treatment fluids are generally hot and~or cool water for rinsing, and a wa~er/surfactant mixture for cleansing. Aqueous cleaning is the preferred method for removing salts and ionic contaminantsO In the semi-aqueous cleanin~ pr~tocol, hydrocarbon solvents ~ontaining one or more surfactants are used as cleaning : ~solvents. Solvent which are useful include, for example, wat~r-miscible alcohols and terpenes.
: ! i30 ISe~i-aqueous cleaning can be used to remove both ionic and organic contaminants. Both protocols allow the cont~minants to be rinsed usin~ water. Surfactants which are useful in the cleansing step of the aqueous and semi-aqueous protocols include most types of anionic, nonionic or cationic surfactants~

W093/06949 PCT/US92/0~15 ~12032~

- 17 ~
If a non-aqueous protocol is used, organic solvents are used in the rinsing and cleaning steps. ~ variety of hydrocarbon solvents can be us~d f or this purpose, including acetone, alcohols and trichloroethane, ~for example. Organic solvents which are particularly useful for cleaning sensitive electronic microparts, for example, are terpene solvents. Terpenes are organic materials which are found in nature in the essential oils of many plan~s. T~rpenes have carbon skeletons made up of isoprene (C~2-C-CH=CH2) units joined together in a regular, head-to-tail configuration. Terpene oompounds include, for example, citronellol, T-terpinene/ isoborneol, camphene 1~ and squalene. Terpenes can be monocyclic (e.gO, dipentene)~ dicyclic ~e.g., pinene) t or acyclic (e.g., myrcene). Terpenes which are particularly useful include t~ose available from Petroferm~, Inc., Fernadina Beach, Florida. Terpene solvents are 0 biodegradable and non-toxic, ~ut many have a pungent : odor which limits their usefulness in most systems~
However, the present system is completely closed, therefore oderous solvents like terpenes can be used.
Other useful solven~s include, or example, photoresist ~ strippers which are a mixture of an aliphatic amide, : such as N-me~hyl pyrrolidone, and an amine~ Use~ul photoresist strippers include those manufactured by Advanced Chemical T~chnologies, Bethlehem, PA. These solvents are hazardous to humans, so exposure ~ust be limited. iThe present totally enclosed system allows these solvents to be used safely.
The terpene solvents are preferably intro~uced into the bottom of the vessel, through valve 40 or 42 and port 24 (Figure 3), and are also drained out through ..... ~, ,, .. . ~ . . . . ~ .. . ... . . .

W~93/06949 PCT/U~92/0~1~
21203~

the bottom of the vessel through por~ 24 into storage tank 58 or 60 for recycling or reuse. Terpenes can be filtered or distilled to remove con~aminants and then reusedg for example.
Once the object has been cleaned using the non-aqueous method, it can be rinsed and dried in the same vessel, without leaving a residue, by filling the vessel and immersing ~he objec~ in an organic solvent which is miscible with the cleaning solvent. The orqanic solvent removes all of the residual cleanin~
solvent from the object, even from the involuted, hard-to-reach surfa~es. The organic solvent rinse is prefer~bly followed by drying using hot organic vapor as descri~ed above, which is added to the vessel under 1~ superatmospheric pressure, that is, under pressure of greater than one atmosphere. Organic solvents which are useful for rinsing and drying this purpose include compounds having the general formula R-O-R' wherein R
and ~' comprise organic substitutes having between about two to ten carbon atoms. Isopropyl alcohol and acetone are particularly preferred~ In the non-aqueous protocol, both organic solvent rinsing followed by organic vapor dryin~ can be used. The drying step an be followed by purgin~ the vessel with a relatively inert gas, such as nitrogen, and/or with a~r~
Whe~her solvent or water is used for the cleaning or rinsing steps will be determined primarily by the : type of object to be cleaned and the type of conta~ination to be remo~ed~ For example, salts and ~: 30 livnic contaminants are bes~ re~oved by an agueous : method. A mixture of ionic and organic contaminants can be remo~ed using a semi-aqueous method, and organic : contaminants can be effectively removed using the non-aqueous method. In addition, some plastic '?

WO93/06949 PCT/US92/0~15 212~32~

-- lg components may be a~tacked by certain solvents and are best cleaned using aqueous liquids. For certain metallic objects, however, the use of water may cause flash corrosion, and are bes~ cleaned using organic 5 liquids.
Ultrasonic or megasonic energy can be supplied, for example, by an ultrasonic or megasonic ~ransducers 16.
The sonic ~ransducers 16 can be positioned by or at~ached to ~he exterior walls of the vessel, thereby 10 allowin~ the sonic energy to be directed at ~he interior of the vessel. The sonic enerqy causes agit tion of the fluid inside the vessel. Ultrasonic energy havin~ a frequency in the range of from about 20 kilohertz (khz) ~o 40 khz is used. Megasonic energy l~ having a fre~uency in the range of from about 0.~
megahertz (mhz) to about loS mhz is used for this purpose. Sonic ~ransducers which are useful in the present inven~ion, for example, those available fro~
~ey Corporation, Bloomfield, Connecticut under the tradename Prosonic~n.
A preferred embodiment of the method of the invention using an aqueous pro~ocol combines the following steps: washin~ the object by surfactant wet ~: processing and sonic cavitation followed by alcohol Yapor dryin~. Generally, ~he surfactant wet processing step and sonic cavitation step are performed simultaneously . The f irst step consists of positioning the object or objects to be cleaned in vessel 12, which is completely enclosed except f or the inlets 22, and 34 30 for ad~nitting and draining ~he fluids. The apparatus is preferzbly designed to induce plug-flow to the fluid flowing into the vessel. The term ~plug-flow~ refers to a liquid flow having a front, transverse to the direction of flow, defined by a generally disc-shaped .. . . . . . . . .. .. . . . ... ..

WO 93/~694g PCI/US92/08415 2:1~032'3 volume of li~auid which contains a concentration gradient produced by the mixing o f two licluids a~ their interface. A configura~ion for impar~ing plug-flow is desc:ribed in detail, for example, in U.S. patent 4,633,893 the teachings of which are hereb~
incorporated herein by reference. The vessel is ~hen closed, and the object is rinsed, wi~h hot water. A
surfactant is injected into the water to form a surfactan~water mixture, and ultrasonic energy is applied to vessel 12 by transducers 16, thereby causing cavit~tion of ~he surfactant/water mixture. For this purpose, ultrasonic transducers can be mounted directly to the processing ~essel, for example. When the ultrasonic energy is applied to the solution in the l~ vessel, cavitation occurs in the solution which is instrumental in cleaning ~he isnmersed component~
Vltrasonic energy is applied for a pericd of time suffici.ent to ensure that the immersed prcduct is tho~nughly cleansedy e~g., 2 to 10 minutes. The time peri~d will depend upon several factors, such as the : configuration of the object, t'he nature of the contaminants to be removed and the degree of contamination. The object îs then rinsed again, :: preferably with a cool water rinse, followed by a hot 2~ water rinse. The ~luids used to trea~ the object are allowe~ to hydraulically fill the vessel from the : bottom thexe~y surrounding the object while minimizing turbulence and thus avoiding the formation of eddies in khe fluids. The term "hydraulically full" as u~ed 0 herein means full of liquid, without gas pockets or phase ~oundaries. Suitable mechanism~ for : accomplishing hydraulic-filling are described, for example, in U.S patent 4,795,497, which is hereby incorporated by reerence.

W~93/06g4g PCT/V~92/08415 212Q32~

The drying step is then performed. In ~he first step of this process, an ispropyl (IP~) alcohol vapor is directed into the top of the vessel, through line 122 and valves 78 and 76~ The vapor is allowed to fi~l the vessel as the hot water from the l'ast rinse is removed, thereby displacing it from the top of the vessel. This alcohol vapor drying step is carried out such tha~ substantially all traces of water are removed from the surface of the component includinq the involu~ed surfaces which are not outwardly exposed. In this step, ~he hot rinse wa~er is drained out as the vessel is filled with the IPA ~apor. Therefore, as the water level descends t the object emerges from the water into the warm, dry IP~ vapor. The rate of descent of 1~ the IPA layer is preferably 2 inches per minute or slower. Without wishing to be bound by theory, it is believed that surface tension at the water/IPA liquid interfare acts to drive partic:Les down and out of the vessel. The IPA vapor condenses on ~h. receding cooler liquid forming a floating layer of IPA~ IPA is miscible with water, but distinct layers are maintained due to the surface tension and density differences between the IPA and water. As the ~PA/water interface progresses downward, strong surface ten~ion forces 2S strip away all traces of rinse liquid and particles.
: ~ The alcohol vapor can be then purged from the vessel by introducing an inert gas, such as nitrogen, through : ~alves 80 and 76.
:: If ncessary or desired, compressed air can be ~njec~ed into t~e vessel through valves 80 and 76 to purge any remaining traces of IPA. This process eliminates the problem of flash oxidation of metal parts, which can oceur when surfaces which are still wet come in contact with air.

.......... . . .. . ... . . . . ... .... .

W093~06949 PCT/US92/0~l~
212~32~

~- 22 -Another embodiment of the method utilizes a semi-aqueous protocol. In this embodiment~ the microparts ~o be ~leaned are placed in vessel 12 and the vessel is sealed. The microparts optionally can be prerinsed with water through sprayheads 26~- The vessel is then filled with a solvent via line 82 to immerse the objects completely. The solvent can contain a surfactant, and/or can be a water-miscible solvent.
Sonic energy is applied to the ~essel. The solvent is drained from the vessel via line 82 and valve 72 if the vessel shown in Figure 1 is used, or through drains 36 and valves 38 if the vessel shown in Figure 2 is us~d.
The objects are rinsed with ho~ water. IPA vapor is then introduced into the vessel as described a~ove directly displacing the hot rinse water. The IPA vapor is purged from ~he vessel with nitrogen, followed by compressed airO
Another preferred embodiment of the method of the ;nvention using a non-aqueous protocol combines the following steps: washing the objec~ with a terpene or : mixture of terpenes, and sonic cavitation followed by removal ~f the terpene solvent:with a miscible organic rinsing liquid, preferably IPA or acetoneO ~he first : step consists of positioning the object in vessel 12 as ;~ 25 described above for the aqueous processing method.
Optionally, the object can ~e pre-cleaned by spraying wa~er or an organic gas or liquid on the parts to remove large dirt particles and oils. The terpene or mixture or terpenes is introduced into vessel 12 : 30 ~hrsugh v~l~e 40 and por~ 24 (Figure 3), until the object is immersed in the solvent. The terpene solvent ~ay contain a surfactant. Megasonic or ultrasonic energy is applied to the liquid in the vessel. Once the cleaning step is complete, the terpene solvent is WO93/Ob949 PCT/US92/0~l5 '212~325 drained back into its reservoir 58 through port 24 and ~alve 40. An optional rinsing step can be performed.
The vessel is filled with the li~uid rinsing solvent, which is admitted through valve 42. The so~vent is selected so that it is miscible with and s~ubilizes the terpene, thereby removing residual terpene from the surfaces of the object. Water can be used to rinse some water-miscible terpenes. However, solvents, including IPA and acetone~ are preferred for this purpose. The solvent is ~hen removed from the vessel by draining it from the vessel through port 24 and through valve 42 into its reservoir 60 for recycling and/or .reuse, or through valve 48 for disposal. Hot organic vapor, preferably IPA, is introduced into the 1~ top of vessel 12 through valves 78 and 76 such that the vapor displaces the terpene or rinsing solvent.
Vessel 12 i5 then purged with nitrogen gas, to remove all traces of the drying solvent or vapor. Vessel 12, optio~ally, is purged with com]pressed air. Following this protocol, the object is ultraclean, that is, substantially all traces of contaminants including those of submicron size have been removed.
Solvents used in the present method can be reused again and again. Terpenes which are used to clean the :~ 25 micropar~s ~an be drained back into the holding tank and:then reused, since terpenes generally retain their cleaning power ~hrough several runs. The terpenes can be filtered by ~lacing a filtering device in the system or can be recycled by outside of the system by dist~lling, for example, and then reu~ed. IPA or other rinsing or drying sol~ents also can ~e reused filtered or recycled. Means for filtering, distilling or recycling organic solvents are well known in the art.

wo93/o694s PCT/US92/O~t5 - ~4 -The combination of washing and/or rinsing of ~he object while applyin~ sonic energy allows the object to be thoroughly cleaned, even if it has involuted surfaces which are not directly exposed to the cleaning liquid and which are hard to reach. For e~a~ple, hard disks used in the computer indus~ry must be free of contaminants down to the submicron level, because the head of a hard disk assembly "floa~s" above the disk a~
a distance of a~o~ 0.5 microns or less. The presence of submicron particles on ~he disk can cause the assembly to "crash~. The present method removes substantially all submicron contaminants.
In order to test the cleaning and drying effectiveness of the system, a ~ariety of microparts 1~ were tested. Parts which were tested included hard disk heads, complex shaped prec:ision par~s, miniature ball bearings and screws. The parts were weighed on a precision balance before and aiter treatment to determine if any wa~er or other liquid was left behind after treatment. The presence of the liquid would increase the net weigh~ of the parts, The results showed that using ~he present apparatus and methods, all liquids were removed even from the most complex : mechanical structures.
Compo~ents were fixtured and placed into a 10-liter : stainless steel vessel chamber where the entire cleaning and drying operation was completed. Fluids sequentially filled the chamber entering via a stationary helical spinner located at the bottom of ~he ~hamber. Ultrasonic transducers, mounted to the sidewalls o~ the vessel chamber, csused cavi~ation of the li~uid surrounding the components thereby enhancin~ -the removal of contaminants. These transducers operate to a maximum o~ 600 watts of power, and are 3~ manufactured by J. M. Ney Company of Bloomfield, CT.

WO 93/06~49 P~/US92/08415 Process fluids flowed in from the bottom through inlet 22 filling the vessel 12 chamber and flowed out the top, through outlet 3 2 as shown in Figure 1 . The chamber was just large enough to hold the p~ar~s to be cleaned~ and was designed such that the fl~uid dynamics of the wa~er and chemicals entering the bottom f illed the chamber as a uniform plug and traverse past the parts to ~e cleaned in a repeatable manner, as described above.
In several of the cleaning cases, a closed loop system, as shown in Figure 1, continuously circula~ed cleaning chemicals for uni:Eormity and agitation.
Chemical injection was accomplished by applying nitrogen gas to pressurized canisters of chemicals as 1~ shown in Figure 2. E~ot w ter .rinsed the challlber at flsw rates of about 1 to 5 gpm. Alternately, in the non-atalleous cleaning processes, no water was used for rinsing. Instead, a drying solYent was used, Following cleaning and rins ing, warm IPA vapor 20 entered the top of the chamber where it condensed on the surface of the cooler, receding liquid, forming a measurable layer of liquid IPA as described in detail abo~e9 At the same time, a pump slowly drained the remaining f luid out the bo~tom of the chamber, through line B2 or 84~ Prior to opening the chamber, nitrogen gas pur~ed any remaining IPA vapor, eliminating the possibililty of flash oxidation.
Various parts f rom a variety of diverse market s~gments were cleaned using the present protocols~ All 30 parts were actual production components which were cleaned and tested either in the manufacturer' s location or in a laboratory. The parts were tested to sht)w the effectiveness of the cleaning equipment by - measuring contaminant removal.

WOg3/06949 P~T/US92/0~15 212032~
.

The primary contaminan~s to be removed from the majority of precision components are ionics, orga~ics and particula~es. Ionics, such as sodium chloride (NaCl~ was removed by deionized water, and residual ionîc material was measured with an ionogr~p~ to dete~mine the total number of equivalents of NaCl inmicrograms (~g). Organics axe non-water soluble films that were removed by solvents, or in some cases, IPA. These were measured by gas chromotography/mass spectrometry (GC/MS~ analysis. Particulate removal was measured by rinsing the part with water and measuring the solu~e with a liquid particle counter (LP¢), Dryness was measured by weighing the sample with an analytical balance prior ~o and after the cleaning.
1~ The part was allowed to cool for several minu~es prior to the measurement.
The following examples illustrate the present invention are not intended to be limiting in any way.

: Disk Drives :: The disk-drive market has shown increasing pressure to condense more information into smaller line widths.
This has created a nsed ~or cleaning all parts having 2~ the potential to release submicron-size particlesJ
Many of the components are smallland intricate with complex involuted surfaces manufactured from a variety of materials. To add to the problem, cleaning must be acc~mplished after assem~ly of many subcomponents. The ! 30 following,is a list a few of the major components comprising a disk~drive assembly:

WO 93/06949 PCr/US92/08415 212~32~

Disk Aluminum or ceramic substrate w/cobal/nickel & plhosphorous layer l::overs Aluminum casting with epoxy paint Flex Cables Captain (polyamid) withlacrylic .
adhesive Actuator comb Aluminum/ magnesium, or plastic E-Block Aluminum actuator assembly with ceramic heads Various 316 SS threaded components 1 0 hardware An aqueous protocol was used to clean these parts.
The surfactant used was a 1% water solution of Ca~,riclean #2 made by Turco Products, Inc. uf Westminster, CA. This was chosen because it contains 15 no chlorides which have deleterious effects on the ceramic heads.
Three parts, are actuator assesr~ly, E block assembly and bumper assembly, were selected to be c~eaned because of their complexity. The parts were 20 weighed wi~h an analytical balance before and after the cleaning operation.
~; Xn the evaluation of other cleaning systems, there :, was dif:f icul~y with drying the parts without leaving water slroplets behinà.
2~ The f ollowing recipe was used:

. Reci~e ~Eor_Cleanin~Disk-Drives Fill Vessel with water and ~ ~ 1% surfactant @ 45C 1 minute : i ~ . i 3 0~ Ssak and apply Ultrasonic ener~y4 minutes m Rinse wafers with DI water @ 50C5 minutes IPA Dry 5 minutes ~2 Purge 1 minute Air Dry 1 minute TOTAL17 minutes , ~
~ ::

WO 93/06949 PCI~/IJS92/û84315 212~32~ ' The results are shown in the f ollowing Tables:
TABLE: A
Actuator As se~ly ~Pre and Post Cleaning) ~~~
Initial Wei~ht Final Weight Net Change (gms) (gms) ~0 5.2Q1 5.201 0.000 5 . ~50 5 ~ 250 0 . 00 5 1 302 5 . 300 -0 . 002 5 . 287 5 . ~8~ ~0 . 003 1~ ~ O 22~ 5 . ~22 -0 . 00 5 . 203 5 . 2~1 -0 . 002 5 . 309 5 . 3~9 0 . 000 5~264 5.263 -~.001 5 . 279 5 . 278 -0 . 0~1 5 . 279 5 . 2~0 ~n . oo~
TABLE B
E-Block Assem~ly ( part of Disc Drive ) 2~
Initial Weight Final ~eight Net Change ( gms ) ( gm5 ) l~
23 . 24 1 23 ~, 246 ~0 . 0~5 23 . 163 23 . 1~8 ~0 . 005 ~3 0 087 23 . 092 ~0 . 005 TABLE C
Bumper AcsembIy : 3~ (Pre and Pos~ C~eaning~
Initial Weigh~ Final Weight Net Change ( gms ) ( ~ms ~ ~
,~o 0.403 0.405 0.0~2 39~ 0.40~ 0.002 0O390 ~ ~.391 0.~01 o ~ 39~ o . 3~9 0 . 001: O ~, 394 0 . 398 ~ . Oû4 0 . 3~6 ~ ~ 396 0 . 00 o . 393 o . 394 0 . ~01 0 . 39 1 0 . 3g2 0 . 001 0.400 0.401 0.001 O 0 394 0 .. 398 0 ~, 00~
0 . 396 0 . 3~ 0 . 001 0 . 39B 0 . 399 0 . 001 ~ . 395 0 . 396 0 . 001 : 0 . 385 o . 3~5 0 . 000 0 . 380 0 . 383 0 . 003 W093/06949 P~T/US92/0~l5 -- 2~2~32~

Example 2 As another example, an assembly consistiny of an electromechanical coil of wire and a spring~l~aded lockin~
device was cleaned using the method. The ~roduct was also cleaned for comparison by conventional methods using FreonT M
vapor degreasers. The ollowing recipe was used:

Recipe Used in Clea~inq Electromechanical Co s Fill Vessel wi~h DI water @ 60C ~ minutes Inject Surfactants to 1/2% concentration 2 minutes ~irculate chemical in ~hamber 1 minute Ultrasonic energy 2 minutes 1~ Rinse with Hot ~I water @ 60C to 10:Meg 10 minutes IPA Dry 15 minutes N2 Purge 3 minutes : TOTAL 40 minutes 2~
The following results were obtained:
T~e number of particles rinsed from the part were : measured with ~ Liquid Par~icle Counter on five samples:

~ A ~ y ~ ~ ~3.1~

: ~ The average cleanliness level for five parts cleaned by each method was mea ured with an Xonograph 500M:
~ 30 : : r onT~ Vapor Deqreaser Aq~eous ~lean W~ y ~ ~ 35,050 particles~5 micron 13,217 particles>5 micron W~93/Ofi94~ PCT/US92/0~15 212032~ `

_ Stainless Steel Screws In another example, 200 stainless stePl screws were placed in a basket to determine the cleaning and drying potential on screws "buried" with close co~act in all dimensionsO The parts were cleaned using the following recipe:

Recipe Used in Cleaning Stainless S~eel Screws lO Fill Vessel with water & 0.5% surfactant @ 60C ~ minutes Ultrasonice Energy 2 minutes Rinse wafers with DI water @ 60C 5 minutes IPA Dry 5 minutes N2 Purge 1 minute 15 Air Dry 1 minute TOTAL 16 minutes ~gai~, the parts were weighed with an ~n lytical balance 20 before and after the cleaning operation. The results are shown in Table D:
TABLE D
Stainless Steel Screws 2~ (Pre and Post Cieaning1 : Initial Weight Final Weight Net Change : (gms~ (gms) 2-56 86.3gl 86.378 -0.013 87.376 87.355 -0.021 83.7?1 ~ 83.767 ~0.004 ! 6l 32 174~507 174.482 -0.025 173.7~4 137.71~ -0.045 172.91~ 172.900 -0.016 .,., . , . ,. .,- ., . ~ ,~ - .~- , . . .

W093/06949 P~T/US92/0~15 212~32~

The post-cleaning weights were reduced significantlyt demonstrating that a measurable number of contaminants were remo~ed from the screws.
,__ . .

Mechanical gyroscopes are manufactured from a variety of metals, plas~ics, epoxies, and insulated wires. The parts 1~ that must be cleaned are small and intricate, and are currently cleaned with FreonTM and 1-1-1 Trichloroethane in ultrasonic degreasersl The real challen~e is in the cleaning snd drying of ~he su~asse~blies, which are suscep~ible to cleaning solutilon remaining in blind holes.
These ass~mblies were cleaned and dried in liquid I~A
~ollowed by vapor phase IPA. The assemblies were weighed with an analytical balance before nd after the cleaning operation. The gyroscopes were clea~ed using the followin~
re~ipe:
2~

: Fill Vessel with liquid IPA @ 60C 2 minutes Ultrasonic at 100% power 2 minutes IPA Dry 4 minutes 2~ N2 ~rge 1 minute Air Dry 1 minute TOTAL 10 minutes The resul~s are shown in Table E:

WO 93/~6949 P~/US92/08~1~
2120~2~ ~

TABLE E
Gyroscope As sembl ies t Pre and Post S~leaning Initi 1 Weight Final Weight ~ Net Change (~ms) tgms~ ~
17 ~2g2 17 o28~i ~0~007 15~832 15~831 0~001 1~ ~L~
Ball bearing assemblies of stainless steel construetion are traditionally cleaned using Freon~ M and 1~
trichlorc~ethalle in vapor de~reasers. Ball bearing : ~ assemblies were cleaned using the present protocol with an 20 aqueous solution with DI water and a surfactant, 0.2%
~mmunol S 6 f rom the Harry Miller Corporation of Philadelphia, PA. The assemblies consisted of a ring shaped annular carrier containing a: series of ball bearings wi~hin the annular ca~ity.
~: The bearings were cleaned usin~ the following recipe :

.
~e Used in C1~3~
Fill Vessel wi~h water ~ 0 . 2% Immunol S-6 @ 65 C 1 mislute Soak and apply Vltrasonic energy 10 minutes Rinse wafers with DI water @ 65C 6 minutes IPA Dry 1 minute N2 Pur~e 2 minutes ~ir Er i 4 minutes :: ~ Y ~ .~

TOT~L 24 minutes . ,, . ,...... ,. ,, . . , , ... ~ , W093/~6949 PCT/US92/O~lS
212~325 The degree of cleaning was determined by visual inspection of the.internal surfaces of the bearing ring after cannibalizing a cleaned ~sse~bly. N~, particulate S contamination should be seen under a 20X ~ower binocular microscope. Secondly, cleaned bearing races were placed under load conditions and tested for torque measurements caused by contaminationO

1~ TA~LE F
Ball Bearings Bearing Race Assemblies of Decreasing Size (Pre and Post Cleaning~

Initial Weight Final Weight Net Change lgms) (gms~ ~
32.003 31.975 -0.028 31~96~ 310g46 -00~16 15.173 15.167 -0.006 15~22~ lS.~13 -0.015 5.715 5.707 -0~08 5.530 5~532 -0.002 ~5 0.526 0.525 -0.001 0.485 0.482 -0.003 The results, shown in Table F, indi~ate that 100% yield was obtained.

Drill Bits :~ Precision drill bits used for drilling prin~ed circuit ; boards were cleaned using the present pro~ocal. Cutting oils and metal shavings must be removed from surfaces l~ft from the machining operation. Precision drill bits are typically ~leaned with FreonT M vapor degreasers. In the present example aqueous based cleaning was done with a surfactant followed by IPA vapor drying, using the following recipe:

WO 93/0~9~9 P~r/US92/~84l5 212032~ ~

Recipe Used in Cleaning Prec sion Drlll Bits Fill Vessel wi~h water & 1% surf actant @ 60C 2 minutes Ultrasonic Energy , 2 minutes Rinse wafers with DI water @ 60~C ~ 5 minutes IP~ Dry 5 minutes N2 Pllrge 1 minute Air Dry l minute TOTAL 1~ minutes In order to eliminate the water rinsing and reduce the recipe time, a non-aqueous rec.ipe usisLg IPA as the rinsing ~nd drying agent and a ~erperle solvent, BIOACT 121 1~ (Pe~roferm, Inc. ) which is a mixture of orange terpenes were used in the cleaning process. The stainless steel rack of carbide drill ~its was dipped into a bath of the BIOACT 121 for five seconds and ~hen immediately placed into the rack into the vessel for cleaning. Liquid IPA was pumped into 2G ~he vessel and lthen ultrasonics were applied to the solukion ~ An IP~ vapor dry was perf ormed as the liquid IPA
drained back into ~he reservoir. The following recipe was used:

2~
Dip in BIOACT 121 5 seconds Fill Ve~sel with lis~uid IPA @ 60C 2 minutes.
Ultrasonic 2 minutes IPA Dry 4 minutes 3 0 N2 Pur e 1 minute g Air Dry _1 minute TOTAL 10 minutes W093/06949 P~T/US9~/0~15 2 1 2 0 3 2 i - 3~ -Cleanli~ess was determined by using a binocular microscope to search for par~iculate left on the drill bit flutes and the shank. An important consideration is the complete xemoval of all residual c3il t espec,ially at thP
points o~ contact with the drill bit and ~e stainless holderO In both recipes, aqueous and non-aqueous, the desired level of cleanXiness was achieved.

10 ~E~
The solvents ~raditîonally used for photoresist stripping of silicon wafers are hiyhly flammable and very aggressive, and therefore handled with care. Photoresist strippers are typically made up of two compon nts t the base l~ solven~ is an alipha~ic amide, such as N-Methyl pyrrolidone, and an amine. The problem is tha~ plasma etching processes use to etch the parts leave chlorine atoms in the vertical profile of the e~ched me~al. When exposed to DI wa~er, acids are formed which etch the aluminum-copper met~l ions.
: 20 ~his is especially pro~lematic in submicron line ~eometry where ritical di~ension loss (CD loss) can etch greater than 0.2 microns, which means that the space between metal lines has increased~
In ~his example a phstoresist compound was used:
ACT~M-CMI-A (manufactured by Advanced Chemical Technologies, IncO of Bethlehem, PA), which is a positi~e resist stripper and is specially formulated for the r~moval of resists on highly corrosion-sensitive me~als and metal alloys. 125mm wafers were coated with photoresist, then cleaned and dried usi~g twoidifferent cleaning techniques. In one run we rinsed the wafers were rinsed with water after the stripping, and in the other IPA vapor was used to dry the stripper without any water. In order to insure that any salts were removed prior to stripping, a rinse and dry 3~ operation preceded the stripping operation.

W093/0694~ P~T/US92/0~5 212032~

The photoresis~ stripping recipes were:
Rinse wafers with DI wa~er ~ 50C 2 minutes IPA Dry 5 minutes ~ill Vessel with ACT-CMI-A @ 75C '~~~ minutes Ultrasonic energy 12 minutes Drain ACT from vessel 2 minutes Rinse wafers with DI water ~ S0C S minutes IPA Dry 10 minutes 10 ~2 Purge 4 minutes TOTAL 42 minutes and Rinse wafers with DI wates @ 50C 2 minutes IPA Dry 5 minutes ~ill Vessel with ACT-CMI-~ @ 75C 2 minutes Ultrasonic energy 12 minutes 20 IPA Dry 10 minutes N2 Purge 4 minutes TOTAL 35 minutes 2~ After cleaning, ~he wafers were tested using microfluoressence to determine whether the resist has been completely removgd~ The CD loss was measured for the water rinse recipe and the IP~ dry recipe with no water rin5ing~
It was determined ~hat t~e recipe with no post etch rinsing had a lower D loss~ In this case the photoresis~ stripper solvent was directly displaced with IPA vapor without the need for a water rinse.

.

W~93/06949 PCT/US9~/0~15 2:~2932~

_ _ Ceramics Ceramics are used for e~erythlng from ~ard disk~dri~es to transducers. They are generally cleanéd using Freon~ M
cleaning operations. In this example, ceramic sonar tranducers were cleaned without the use of an aqueous cleaner ~ecause the ceramics absorb water which distorts the resonance of the transducer. ~fter cleaning and drying, the entire unit is encapsulated in an epoxy to prevent wa~er from entering the pores of the ceramic. The following complete solvent clean and dry recipe was used:

Reci~ Used in Cleaning Cerami.cs 1~ Fill Vessel with li~uid IPA @ 60C 2 minutes Ultrasonic at 100% power 2 minutes IP~ Dry 4 minutes N2 Purge 1 minute Air Dry 1 minute : : TOTAL 10 minutes Heated liquid IPA filled ~he vessel and immersed the ~ransducers~ ~hen ultrasonics was used to help remove external contaminants. An IP~ vapor dry insured that components were completely dry. This process completely.
eliminated the need for FreonTM ~s by replacing them with IPA
uid and vapor. Simultaneously~ it insured that no water was absor~ed into the hydroscopic ceramic surface.

W~93/06949 P~T/US92/0~15 212032~

E~uivalents One skilled in the ar~ will be able to ascertain many equivalents to the specific embodimen~s de cribed herein.
Such equivalents are intended to be encompassed by the scope of the following claimsO

Claims

-39-1. A method for cleaning surfaces of an object having an involuted configuration, comprising the steps of:
a. placing the object to be cleaned in a sealable, air-tight, enclosed treatment vessel having at least one fluid sealable port located at the bottom of the vessel the object being held stationary in a fixed position within the vessel;
b. filling the vessel with washing fluid to immerse the object thereby contacting all of the involuted surfaces with washing fluid;
c. exciting the washing fluid in the vessel with sonic energy;
d. filling the vessel with rinsing fluid to immerse the object thereby contacting all of the involuted surfaces with rinsing fluid; and e. removing rinsing fluid from the surfaces of the object by contacting said surfaces with a drying solvent such that substantially no rinsing fluid droplets are left on the involuted surfaces of the object after removal of the rinsing fluid.
2. The method of Claim 1 wherein the sonic energy is ultrasonic energy having a frequency of from about 20 to about 40 khz.
3. The method of Claim 1 wherein the sonic energy is megasonic energy having a frequency of from about 0.8 to about 1.5 mhz.
4. The method of Claim 1 wherein the washing and rinsing fluids comprise aqueous fluids.
5. The method of Claim 4 wherein the aqueous washing fluid contains a surfactant.
6. The method of Claim 1 further comprising the step of circulating the fluid through the vessel.
7. The method of Claim 1 wherein the drying solvent is in vapor form and wherein step e is performed by displacing the rinsing fluid from the vessel by filling the vessel from the top with the drying vapor as the rinsing fluid is being drained out the bottom so that the object emerges from the rinsing fluid directly into the drying vapor.

8. The method of Claim 7 wherein the displacing step is conducted at superatmospheric pressure.
9. The method of Claim 1 wherein the drying solvent is in liquid form and wherein step e is performed by removing the rinsing fluid from the vessel, filling the vessel with the drying solvent so that the object is immersed in the drying solvent, and draining the solvent out of the vessel at a rate which maintains surface tension of the drying solvent to avoid leaving droplets, thereby causing substantially all traces of the rinsing fluid to be removed from the surfaces of the object.
10. The method of Claim 1 wherein the drying solvent is a compound having the formula R-O-R', wherein R
comprises an organic radical having between 2 to about 10 carbon atoms and R' comprises an organic radical having between 2 to 10 carbon atoms or hydrogen.
11. The method of Claim 10 wherein the drying solvent comprises isopropyl alcohol or acetone.
12. The method of Claim 1 further comprising the step of purging the vessel of the drying solvent after step e.
13. The method of Claim 12 wherein the purging step is performed by introducing an inert gas into the vessel.

14. The method of Claim 13 wherein the inert gas comprises nitrogen or argon.
15. The method of Claim 1 wherein the washing or rinsing fluid comprise organic solvents.
16. The method of Claim 15 wherein the washing fluids comprises terpenes.
17. The method of Claim 15 wherein the rinsing liquid comprises isopropyl alcohol or acetone.
18. The method of Claim 15 further comprising the step of recovering the organic solvents and storing them for reuse.
19. The method of Claim 1 further comprising the step of spraying the object with a precleaning liquid prior to step b.
20. A method for cleaning surfaces of an object having an involuted configuration comprising the steps of:
a. placing the object to be cleaned in a sealable, air-tight enclosed treatment vessel having at least one fluid sealable port located at the bottom of the vessel the object being held stationary in a fixed position within the vessel;

b. filling the vessel with an aqueous cleaning liquid to immerse the object thereby contacting all of the involuted surfaces with the aqueous liquid;
c. applying sonic energy to the aqueous liquid in the vessel;
d. immersing the object in an aqueous rinsing liquid to remove traces of the washing liquid;
and e. removing the rinsing liquid on the surfaces by exposing the object to a non-aqueous drying solvent.
22. The method of Claim 20 wherein the sonic energy is megasonic energy having frequency of from about 0.8 to about 1.5 mhz.
23. The method of Claim 20 wherein the sonic energy is ultrasonic energy having a frequency of from about 20 to about 40 khz.
24. The method of Claim 20 wherein step e is performed by exposing the surfaces to a hot alcohol vapor which combines with droplets of the aqueous rinsing liquid on the surfaces and removing the rinsing liquid-alcohol combination by evaporation from the surfaces.

25. The method of Claim 20 wherein the drying solvent is an ambient temperature water-miscible alcohol and step e is conducted by removing droplets of the aqueous rinsing liquid from the surfaces by formation of a mutual solution of the alcohol and the droplets.
26. A method for cleaning surfaces of an object comprising the steps of:
a. placing the object to be cleaned in a sealable, air-tight, enclosed treatment vessel having at least one fluid sealable port located at the bottom of the vessel the object being held stationary in a fixed position within the vessel;
b. filling the vessel with an organic cleaning liquid thereby immersing the object in the cleaning liquid;
c. applying sonic energy to the organic cleaning liquid in the vessel;
d. removing the organic cleaning liquid from the surfaces of the object by filling the vessel with a drying solvent under conditions sufficient to leave substantially no trace of the cleaning liquid on the surfaces of the object; and e. contacting the surfaces of the object with an inert gas.

28. The method of Claim 26 wherein the sonic energy is ultrasonic energy having a frequency of from about 20 to about 40 khz.
29. The method of Claim 26 wherein the sonic energy is megasonic energy having a frequency of from about 0.8 to about 1.5 mhz.
30. The method of Claim 26 wherein the organic cleaning liquid comprises a terpene or a mixture of terpenes.
31. The method of Claim 26 further comprising the step of contacting the object to be cleaned with a rinsing liquid to remove traces of the organic liquid from the surfaces of the object after step b.
32. The method of Claim 31 wherein the rinsing liquid is an organic compound having the general formula R-O-R' wherein R comprises an organic substituent having between 2 to 10 carbon atoms and R' comprises an organic substituent having between 2 and 10 carbon atoms or a hydrogen atom.
33. The methods of Claim 32 wherein the organic rinsing liquid comprises isopropyl alcohol or acetone.
35. The method of Claim 26 wherein step is performed by introducing a hot organic solvent in vapor form into the vessel.

36. The method of Claim 35 wherein the organic vapor is introduced so that it displaces the rinsing liquid from the vessel.
37. The method of Claim 35 wherein the organic vapor comprises isopropyl alcohol vapor.
38. The method of Claim 26 wherein the inert gas comprises nitrogen gas.
39. The method of Claim 26 further comprising the step of purging the vessel with air following step e.
40. Cleaning apparatus comprising:
a. a sealable, air-tight, treatment vessel for enclosing at least one object to be cleaned a first fluid sealable port located a the bottom of the vessel;
b. means for immobilizing the objects within the vessel;
c. means for passing serially a flow of a cleaning or rinsing liquid through the port into the enclosure and about objects to be cleaned disposed therein;
d. means for exciting the liquid in the vessel with sonic energy; and e. means for removing the cleaning or rinsing liquid in contact with objects disposed within the enclosure, said means for removing comprising means for introducing into the enclosure an organic drying solvent for the cleaning or rinsing liquid and which does not leave a residue on the object.
41. The apparatus of Claim 40 wherein the cleaning rinsing liquid comprises a photoresist stripping solvent.
42. The apparatus of Claim 40 further comprising:
e. means defining a second port, located at the top of the vessel for introducing organic solvent vapor and gases into the enclosure.
43. The apparatus of Claim 41 further comprising means for introducing a vapor into said vessel under sufficient pressure to displace the cleaning or rinsing liquid contained in the vessel.
44. The apparatus of Claim 40 further comprising valve means for maintaining a superatmospheric pressure within the enclosure.
45. The apparatus of Claim 40 wherein said means for introducing an organic drying solvent comprises means for introducing liquid isopropyl alcohol or acetone.

46. The apparatus of Claim 40 wherein said means for introducing an organic drying solvent comprises means for introducing isopropyl alcohol or acetone in vapor form.
47. The apparatus of Claim 40 further comprising spray means for introducing a liquid spray into the enclosure.
48. The apparatus of Claim 40 further comprising means for recovering the organic drying solvent from said vessel and a tank for storing the solvent for reuse.
49. The apparatus of Claim 40 further comprising means for passing is means for passing terpenes.
50. The apparatus of Claim 40 further comprising means for recycling terpenes.
51. A method for removing photoresist from an object comprising the steps of:
a. placing the object to be cleaned in a sealable, air-tight, enclosed treatment vessel having at least one fluid sealable port located at the bottom of the vessel the object being held stationary in a fixed position within the vessel;

b. filling the vessel with an organic photoresist stripping solvent thereby immersing the object in the solvent;
c. applying sonic energy to the solvent in the vessel; and d. removing the photoresist stripping solvent from the surfaces of the object by filling the vessel with a drying solvent under conditions sufficient to leave substantially no trace of the stripping solvent on the surfaces of the object.
52. The method of Claim 51 wherein the sonic energy is ultrasonic energy having a frequency of from about 20 to about 40 khz.
53. The method of Claim 51 wherein the sonic energy is megasonic energy having a frequency of from about 0.8 to about 1.5 mhz.
54. The method of Claim 51 wherein the photoresiststripping solvent comprises N-methyl pyrrolidone.
54. The method of Claim 51 further comprising the step of contacting the object to be cleaned with a rinsing liquid to remove traces of the stripping solvent from the surfaces of the object after step b.

55. The method of Claim 54 wherein the rinsing liquid is an organic compound having the general formula R-O-R' wherein R comprises an organic substituent having between 2 to 10 carbon atoms and R' comprises an organic substituent having between 2 and 10 carbon atoms or a hydrogen atom.
56. The methods of Claim 55 wherein the organic rinsing liquid comprises isopropyl alcohol or acetone.
57. The method of Claim 51 wherein step d is performed by introducing a hot organic solvent in vapor form into the vessel.
58. The method of Claim 57 wherein the organic vapor is introduced so that it displaces the rinsing liquid from the vessel.
59. The method of Claim 57 wherein the organic vapor comprises isopropyl alcohol vapor.
60. The method of Claim 51 further comprising the step of contacting the surfaces of the object with an inert gas after step d.