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Title:
METHOD, APPARATUS, AND COMPOSITION FOR DRYING SOLID ARTICLES
Document Type and Number:
WIPO Patent Application WO/2001/042727
Kind Code:
A3
Abstract:
Disclosed herein is an apparatus, method and drying agent composition for drying solid articles such as semiconductor wafers. The dryer (10) comprises a process tank (12) and a drying fluid supply system (100). The process tank (12) includes a plurality of spray nozzles (15) to spray a non-flammable drying fluid to wet surfaces of the article for drying without the necessity of heat or other external means. The drying fluid comprises a non-flammable, environmentally compatible, and non-hazardous fluid including a drying agent of hydrofluoroether and a surfactant of isopropyl alcohol. Even without the benefit of heating, little if any solution or static charge remains after drying. The dryer (10) includes a drying fluid supply system (100) for providing the drying fluid to the plurality of spray nozzles. The drying agent composition comprises a mixture of hydrofluoroether and a tertiary alcohol such as tertiary butyl alcohol.

Inventors:
BETTCHER DEAN (US)
KUBINSKI CHRISTOPHER (US)
FUGATE THOMAS V (US)
Application Number:
US2000/033115
Publication Date:
March 06, 2008
Filing Date:
December 06, 2000
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
CALTEK SALES (US)
BETTCHER DEAN (US)
KUBINSKI CHRISTOPHER (US)
FUGATE THOMAS V (US)
International Classes:
F26B5/04; H01L21/00
Foreign References:
US5369891A1994-12-06
US5551165A1996-09-03
US6048832A2000-04-11
US3710450A1973-01-16
US5985041A1999-11-16
US5950328A1999-09-14
US5974689A1999-11-02
US6159917A2000-12-12
US6187107B12001-02-13
US6187954B12001-02-13
Attorney, Agent or Firm:
CHAIKIN, Douglas, A. et al. (2290 North First Street Suite 10, San Jose CA, US)
Download PDF:
Claims:

CLAIMS 1. An apparatus for drying solid articles, comprising: a process tank having a spray member; a platform member for holding an article to be dried in the tank; a spray member for applying, by spraying, a drying fluid including a drying agent in combination with a surfactant to the article to be dried; the drying agent comprising HFE and the surfactant including an alcohol based product; and a drying fluid supply system connected to the spray member for supplying drying fluid to the spray member, whereby article is dried by spraying of a drying agent in combination with a surfactant.
2. The drying apparatus as recited in claim 1, wherein the drying fluid comprises a surfactant of an amount of IPA insufficient to make the drying fluid flammable and the remainder the drying agent of HFE.
3. The drying apparatus as recited in claim 1, wherein the drying fluid comprises between 0.01% and 15% IPA and the remainder HFE.
4. The drying apparatus as recited in claim 1, wherein the drying apparatus includes a system for recovering the drying fluid.
5. The drying apparatus as recited in claim 4, wherein the drying apparatus includes a recycling system for recycling the HFE in the drying apparatus.
6. The drying apparatus as recited in claim 2, wherein the drying apparatus includes a recycling system for recycling the IPA in the drying apparatus.
7. The drying apparatus as recited in claim 1, wherein the drying apparatus includes a spiking system for spiking the drying apparatus.

8. The drying apparatus as recited in claim 1, wherein the drying apparatus includes a condensation prevention system.
9. The drying apparatus as recited in claim 1, wherein the drying apparatus includes a reservoir of drying agent, a supply line between the spray members and the reservoir and in line heating unit between the spray members and the reservoir.
10. The drying apparatus as recited in claim 1, wherein the drying apparatus includes a separation tank for separating the drying agent and the surfactant, the separation tank including a separation filter for creating surface tension to facilitate separation of the mixture of the drying agent and the surfactant from the water.
11. The drying apparatus as recited in claim 10, wherein the separation filter system comprises: a perforated filter, a pump coupled to the separation tank for pumping the drying fluid from the separation tank to the drying fluid supply system; and one or more filters coupled between the pump and the drying fluid supply system to filter the drying fluid pumped from the separation tank to the drying fluid supply system.
12. The drying apparatus as recited in claim 1, wherein the drying apparatus includes a compressed dry air supply system coupled to a plurality of spray nozzles for forcing the drying fluid through the plurality of nozzles.
13. The drying apparatus as recited in claim 1, wherein the process tank includes at least one wall panel heater for heating the ambient fluid of the process tank 14. A method of drying solid articles including the steps of fixing the articles to be dried in a process tank; applying a drying fluid by spraying to the articles in the process tank, wherein the drying fluid including a drying agent of HFE and a surfactant of an alcohol based product, such that the drying fluid is not flammable;

extracting the drying fluid from the tank; and separating the drying agent from the extracted drying fluid.

15. The method as recited in claim 14, wherein the step of recycling the drying agent from the extracted drying fluid for the reuse is included.
16. The method as recited in claim 1, wherein the step of heating the drying agent prior to spraying is included.
17. The method as recited in claim 14, wherein the surfactant comprises between 0.01% and 15% of the drying fluid and the remainder being the drying agent.
18. The method as recited in claim 14, wherein the following steps are included: providing the process tank with at least one panel heater; heating the process tank during spraying of the drying fluid; providing the process tank with a condensation prevention system; after spraying, passing the article to be dried through the condensation prevention system.
19. A drying agent composition for drying solid articles, comprising: a mixture of a hydrofluoroether; and an alcohol, whereby said article is dried by contact with the drying agent composition.
20. The drying agent composition as recited in claim 19, wherein the tertiary alcohol is tertiary butyl alcohol.
21. The drying agent composition as recited in claim 19, wherein the hydrofluoroether is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
22. The drying agent composition as recited in claim 20, wherein the drying agent composition comprises between 0.1 % and 15% butyl alcohol and the remainder hydrofluoroether.

23. The drying agent composition as recited in claim 19, wherein the hydrofluoroether is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
24. The drying agent composition as recited in claim 19, wherein the drying agent composition comprises between 0.1 % and 15% isopropyl alcohol and the remainder is hydrofluoroether.
25. A drying agent composition for drying solid articles, comprising: a mixture of one or more hydrofluoroethers; and one or more alcohols, whereby said article is dried by contact with the drying agent composition.
26. The drying agent composition as recited in claim 25, wherein one of the hydrofluoroethers is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
27. The drying agent composition as recited in claim 25, wherein one the alcohols is a mixture of n- butyl alcohol and alcohol selected from the group consisting of isopropyl alcohol and n-propyl alcohol.
28. A drying agent composition for drying solid articles, comprising: a mixture of one or more hydrofluoroethers; and one or more polyhydric alcohols, whereby said article is dried by contact with the drying agent composition.
29. The drying agent composition as recited in claim 28, wherein one of the hydrofluoroethers is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
30. The drying agent composition as recited in claim 28, wherein the polyhydric alcohol is a mixture of propylene glycol and alcohol selected from the group consisting of n-propyl alcohol, n- butyl alcohol, n-propyl alcohol, and ethylene glycol.

31. A drying agent composition for drying solid articles, comprising: a mixture of a hydrofluoroether, hydrofluoric acid; and an alcohol, whereby said article is dried by contact with the drying agent composition.
32. The drying agent composition as recited in claim 31, wherein the hydrofluoroether is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
33. The drying agent composition as recited in claim 31, wherein the drying agent composition comprises between 0.1% and 15% butyl alcohol, between 0.1% to 5.0% hydrofluoric acid and the remainder hydrofluoroether.
34. The drying agent composition as recited in claim 31, wherein the hydrofluoroether is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
35. The drying agent composition as recited in claim 31, wherein the drying agent composition comprises between 0.1% and 15% isopropyl alcohol, between 0.1% to 5.0% hydrofluoric acid and the remainder is hydrofluoroether.
36. The drying agent composition as recited in claim 31, wherein the drying agent composition comprises between 0.1% and 15% isopropyl alcohol, between 0.1% to 5.0% hydrofluoric acid and the remainder is methoxy nonafluorobutane.
37. A drying agent composition for drying solid articles, comprising: a mixture of one or more hydrofluoroethers, hydrofluoric acid; and one or more alcohols, whereby said article is dried by contact with the drying agent composition.

38. The drying agent composition as recited in claim 37, wherein one of the hydrofluoroethers is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
39. The drying agent composition as recited in claim 37, wherein one the alcohols is a mixture of n- butyl alcohol and an alcohol selected from the group consisting of isopropyl alcohol, n-propyl alcohol, and propylene glycol.
40. A drying agent composition for drying solid articles, comprising: a mixture of one or more hydrofluoroethers, hydrofluoric acid; and one or more polyhydric alcohols, whereby said article is dried by contact with the drying agent composition.
41. The drying agent composition as recited in claim 40, wherein one of the polyhydric alcohols is propylene glycol.
42. The drying agent composition as recited in claim 41, wherein one of the hydrofluoroethers is selected from the group consisting of methoxy nonafluorobutane and ethoxy nonafluorobutane.
43. The drying agent composition as recited in claim 40, wherein the polyhydric alcohol is an alcohol selected from the group consisting of n-propyl alcohol, n-butyl alcohol, and ethylene glycol.
44. The drying agent composition as recited in claim 40, wherein the drying agent composition comprises between 0.1 % and 15% propylene glycol, between 0.1 % to 5.0% hydrofluoric acid and the remainder is hydrofluoroether.
Description:

SPECIFICATION METHOD, APPARATUS, AND COMPOSITION FOR DRYING SOLID ARTICLES CROSS-REFERENCE TO RELATED APPLICATIONS: Reference is made to a priority claimed from U. S. Provisional Application Serial No.

60/172, 850, filed December 10,1999, titled"Compositions for drying solid articles"and U. S.

Provisional Application Serial No. 60/172,853, filed December 10,1999, titled"Compositions for drying solid articles,"and reference is made to U. S. Patent No. 6,128,830 issued on October 10,2000.

Background of the Invention: Field of the Invention: The present invention relates generally to the field of drying solid articles such as optical, electronic, semiconductor and other surfaces, such as liquid crystal displays, magnetic media hard drive components and wafers and more particularly to a method, apparatus and a drying agent composition for drying solid articles.

Background : In the manufacture of computer components it is often required that components such as thin film read-write heads components, computer peripherals, and semiconductor wafers are free of contaminants and aqueous residues. For example, in semiconductor wafer processing, the wafers often exit various processing stages where water and aqueous residues are present on the wafer. It is undesirable to allow the aqueous solutions to flash dry so as to leave residuals and/or stains on such articles at the end of the drying process. Such residuals on semiconductor wafers and like solid articles create contaminants that negatively impacts yields of semiconductors wafers and like solid articles. The residue stains and/or contaminants degrade the performance of such articles and/or interfere with a subsequent processing step.

Various known processes have been developed in an attempt to dry the wafers and similar solid articles in a manner that removes the aqueous residue, and stains, and contaminants and static without damaging or adding contaminates to the wafer or similar solid articles. One such example of a known drying process incorporates external forces in a Spin Rinse Dryer technique, SRD. SRDs use centrifugal force to cause the aqueous residue and contaminant molecules to spin off ; not altogether that different from a domestic dryer unit. SRDs are inherent residual particle generators. The residual particulate matter is formed from the mechanics of the system and the vibration of the wafer carrier.

As the wafer and carrier spin, it causes the build up of static electricity. As the surface of the article changes from a wetted state to a dry state, it becomes statically charged. The change in electrostatic state attracts more airborne particulates and consequently more contamination.

The performance of the article is thereby further degraded. The production yield of usable articles will further decrease because of tribolelectric charging on the article as the result of the article being statically charged.

Increasingly, there is a decreasing dimension of line widths and structure geometries on wafers. Particulate contamination is critical to fine geometries in the sub-0.3 i area. It has been noted that SRD systems have substantial difficulty cleaning particulates below 0.3 u.

Accordingly, such SRD systems are no longer an acceptable solution to the drying needs of the semiconductor or similar industries that require fine geometries.

Another external force dryer is known as an air knife dryer. This dryer includes a plane of forced air upon the exit of the process of the article. The forced air drying, like the spin dry technique is effective but not for the smaller particles. For particulates of less than 0.5, forced air drying will be ineffective. Similar to the SRD drying technique, the air knife leaves a trail of airborne particulates and statically charged particles, which promote the accumulation of contamination on the article to be dried.

Another category of dryer for such solid articles is the liquid solubilization, also known as a vapor drying process. Generally vapor dryers utilize an open vat of boiling alcohol or isopropyl alcohol (IPA) within a chamber. Alcohol vapor forms in the chamber above the boiling alcohol vat. The temperature of the vapor is approximately the same temperature as the alcohol in the vat. An article at ambient temperature, such as a wafer, is introduced into the chamber. Since the wafer is cooler than the vapor temperature, the alcohol vapor condenses on the wafer and creates a flushing action, which acts to remove aqueous residues and contaminants from the surface of the wafer. The condensed alcohol and residues are then collected and recirculated. Eventually, however, the temperature of the vafer begins to approach that of the

alcohol vapor. When this occur :, the condensation and flushing action slows until very little aqueous residue or contaminants are removed. Thus, the efficiency of the process is evaluated by the amount of alcohol that can condense on the wafer prior to the wafer coming to vapor temperature. Additionally, if the wafer has very little thermal mass, it is possible for the aqueous residue and contaminants to quickly evaporate (flash dry) on the wafer due to the heat in the chamber and have very little removed by any formed condensation. Thus, a limitation of this technique is the ability to condense alcohol on the wafer to produce a flushing action and yet not remove any residues or contaminants on the wafer.

The use of vapor drying processes also present several other considerations. The systems generally use large amounts of IPA, a flammable agent, a boiling sump, or vat, and coiling coils to assist in condensing the vapors on the wafer. The use of the open alcohol vat utilizes a large amount of fluid due to evaporation of the alcohol over the large surface of the vat. The separation of the aqueous residues from the alcohol is generally accomplished by distillation of the alcohol from the water through an alcohol reprocessor. These expensive reprocessors are generally located in the same processing area and present issues of safety due to the highly flammable nature of the agents. Also, vapor emissions must be removed from the facility. Often this is accomplished using a burn box (scrubber) on the building, which burns off the emissions. The use of a burn box or scrubber also presents a high safety risk as well as a greatly increased equipment expense.

As noted above, vapor drying processes present serious safety and environmental concerns. Even under the best of circumstances where there are no accidents, the costs of insurance will be quite high and add to the costs of manufacture.

Environmental and safety concerns are clearly quite high with a pot of boiling alcohol.

Additionally, IPA is regulated as a volatile organic compound by the U. S. Environmental Protection Agency. Thus, despite IPA's superior cleaning properties, there are serious safety, environmental and financial concerns. Considering the risks it is desirable to seek other more attractive alternatives.

Another drying process is known as the Capillary Induced Removal (CIR) process. An example of this process is the Marangoni drying process. The Marangoni process removes aqueous residues using surface tension properties. In this process, an article is placed in a vat of water. A very thin layer of IPA is applied on top of the water. The difference in surface tension between the IPA and water creates a reverse meniscus on the article. When the article is slowly removed from the vat, the alcohol acts as a forcing function to drive the aqueous residue off the part. This procedure is limited in that the article must be removed from the vat very slowly so

that surface tension is not broken. If the article is pulled out too quickly, the surface tension breaks and water ends up on the article and the article is contaminated. The process works best on planar geometries and requires a slow removal time. Thus, this procedure is not efficient for drying wafers and other articles with complex geometries, or non-planar geometries or where high-throughput of wafers is required.

Displacement drying is yet another process for drying semiconductor wafers and other solid articles. The article has a film of water and that film must be removed before the manufacturing process is complete or the article finished. In this process, the water-filmed article is treated with a volatile methyl siloxane (VMS) that contains a surfactant. The VMS/surfactant displaces the water film leaving a surfactant film in its place. VMS is then used to remove the surfactant. Clearly having two steps is a serious disadvantage of the displacement drying process. Additionally, many VMS chemicals are flammable and present safety and environmental hazards as well. The additional step of rinsing off the film cuts down yield and adds consequently to the costs of manufacture. Additional costs include the environmental and safety costs, again adding to manufacturing costs.

What is needed is an apparatus and process which dries articles quickly and thoroughly and adds to the production yield over presently known methods, rather than decrease production yields. Additionally, such apparatus and method must pose the smallest possible risk to the environment and to the safety of all involved in the manufacturing process. What is also a needed such an apparatus and process that eliminates even ultra small particulates from the surface of the article without generating charged particles.

What is needed is a drying agent composition which dries articles quickly and thoroughly and adds to the production yield over presently known methods, rather than decrease production yields. Additionally, such drying agent composition must pose the smallest possible risk to the environment and to the safety of all involved in the manufacturing process.

SUMMARY OF THE INVENTION It is an object of this invention to provide a novel drying apparatus, which dries solid articles using an environmentally sound, and worker friendly method and products.

It is an additional object of this invention to provide a compound for use in such a drying apparatus which provides environmentally sound and worker friendly condition while increasing net yields of manufacture of the article and while drying articles more thoroughly and more cost effective than presently known methods.

It is an additional object of this invention to provide a novel method of drying solid articles, which can be used to produce greater yields with less statically charged particulates and flammability considerations.

It is an object of this invention to provide a novel drying agent composition, which dries solid articles using environmentally sound, and worker friendly products.

It is an additional object of this invention to provide a drying agent composition for use in a drying apparatus which provides environmentally sound and worker friendly condition while increasing net yields of manufacture of the article and while drying articles more thoroughly and more cost effectively than presently known methods.

It is an additional object of this invention to provide a drying agent composition for use in a drying apparatus which does not adversely affect the surfaces to be dried and provides environmentally sound and worker friendly condition while increasing net yields of manufacture of the article and while drying articles more thoroughly and more cost effectively than presently known methods.

It is an additional object of this invention to provide a drying agent composition for drying solid articles, which can be used to produce greater yields with less statically charged particulates and reduced flammability considerations.

In accordance with the above objects and those that will be mentioned and will become apparent below, the drying apparatus in accordance with this invention comprises: a process tank having a spray member; a platform member for holding an article to be dried in the tank; a spray member for applying, by spraying, a drying fluid including a drying agent in combination with a surfactant to the article to be dried; the drying agent comprising HFE and the surfactant including an alcohol based product; and a drying fluid supply system connected to the spray member for supplying drying fluid to the spray member, whereby article is dried by spraying of a drying agent in combination with a surfactant.

In accordance with the above objects and those that will be mentioned and will become apparent below, the drying agent composition in accordance with this invention comprises: a drying agent composition for drying solid articles, comprising: a mixture of hydrofluoroether ; and alcohol, wherein the term"hydrofluoroether"includes mixed hydrofluoroethers and the term"alcohol"includes mixed alcohols and polyolys; and

whereby said article is dried by contact with the drying agent composition. Depending upon the quantity (mass) of the articles to be dried, the alcohol content can be increased or decreased to increase or decrease the drying time.

It is an advantage of this invention to a provide a method of drying an article such that the article is thoroughly dried using a one step process.

It is an additional advantage of this invention to a provide a method of drying an article such that the article is thoroughly dried using a one step process using a method and compound that are environmentally safe and worker friendly.

It is an additional advantage of this invention to a provide a method of drying an article such that the article is thoroughly dried using a one step process, using a method and a compound that are environmentally safe and worker friendly, while at the same time increasing the yields of manufacturing such articles over presently known methods.

It is an additional advantage of this invention to a provide an apparatus and method of drying an article such that the article is thoroughly dried using a one step process using a method and a compound that are environmentally safe and worker friendly, while at the same time providing an apparatus which relatively inexpensive, easy to maintain and increases yields over presently known methods and apparatus.

Brief Description of the Drawing : For a further understanding of the objects and advantages of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawing, in which like parts are given like reference numerals and wherein: Fig. I is a schematic representation of the apparatus and method of drying articles in accordance with this invention.

Fig. 2 is a detailed schematic representation of the process tank in accordance with the apparatus in accordance with this invention.

Detailed Description of the Invention The drying apparatus and method in accordance with this invention processes solid articles, including, but not limited to semiconductor wafers. The drying apparatus and method removes aqueous solutions from solid articles without adding static or statically charged particulates or other contamination or stains. In one embodiment, the drying apparatus comprises a process tank and a drying fluid supply system. The process tank includes a spray member having multiple spray nozzles for spraying a non-flammable drying fluid onto the

surfaces of the article. In one embodiment the drying apparatus is top loading and in another embodiment the drying apparatus is front loading.

In another embodiment, the drying fluid comprises a drying agent and a surfactant. The drying fluid is non-VOC material, which leaves no residual residue on surfaces of the article after being sprayed on the article for drying. In another embodiment, the drying agent comprises hydrofluoroether (HFE) and the surfactant comprises isopropyl alcohol (IPA). A compressed dry air supply, compressed nitrogen supply, or a gas may be used to force the drying fluid through the spray nozzles.

The drying fluid supply system provides the drying fluid to the spray nozzles using a supply line connected to a reservoir of drying fluid. In one exemplary embodiment, the drying fluid supply system is capable of adding more drying agent and/or more surfactant to the drying fluid via an in-situ spiking mechanism.

In another exemplary embodiment, the drying apparatus and method in accordance with this invention includes a separation tank and a waste tank. After spray drying a mixture is formed which includes the contaminants and aqueous products, the surfactant and the drying agent. Upon mixing the surfactant with water, the surfactant with the water is no longer soluable in the drying agent. As will be appreciated, this aids in separating the drying agent from the rest of the mixture.

The mixture including the drying agent is sent through a primary filter between the process tank and the waste and separation tanks after spray drying. The drying agent is sent to the separation tank, while the rest of the mixture is received as discharge by the waste tank.

After separating drying agent from the rest of the mixture, i. e. the surfactant and other products, the drying agent in the separation is pumped through a series of filters to further purify the used drying agent. Upon a successful filtration process, the drying agent may be recirculated to the drying fluid supply system for use in subsequent drying operations.

The separation tank of this embodiment comprises a separation filter (e. g., an encapsulated perforated filter) that creates surface tension to facilitate separation of the mixture of the drying agent from the surfactant and from the water.

It should be noted that the HFE and the IPA with adequeous products (after spray drying) do not mix so that separation is encouraged based upon the selection of those chemical materials in conjunction with a thorough understanding of the method of drying in accordance with this invention. Additionally, the density difference between the HFE and IPA with aqueous products causes the HFE to sink alone to the bottom of the separation tank and to be collected there for additional filtering. A pump pumps the separated HFE through a series of filters for

cleaning any impurities and then back to the reservoir for re-use in the supply system drying agent.

The invention will now be described with respect to Fig. 1, which illustrates a preferred embodiment of the invention, an apparatus for drying solid articles shown generally by the numeral 10. The drying apparatus 10 includes a process tank 12 having a spray member 14 and a platform 16 upon which the articles are stationed for spraying. The process tank 12 includes at least one panel heater 17 for heating the ambient environment within the process tank 12.

The process tank 12 is made from stainless steel or electro-polished stainless steel.

Typically, the process tank is sized for the application.

The drying apparatus 10 includes a condensation prevention system 18 for preventing the dried articles from forming condensation as it is moved from the process tank 16 to the ambient environment outside of the process tank 16. The condensation prevention system 18 includes a series of coils 24. The coils 24 are positioned so that after drying the articles, the articles must be pass through the coils 24.

The coils 24 contains a cooling fluid, preferably water, which is chilled by a device such as in-line chiller unit within the drying apparatus 10 for"in-house"chilling. The temperature of the cooling fluid may be adjusted to the temperature desired to prevent even small amounts of condensation from the articles upon being dried.

While not required in accordance with the apparatus and method of the invention, it is often desirable to heat the ambient air surrounding the articles to be dried before drying as well as heating drying fluid. This has the effect of breaking the surface tension of a wetted surface and allowing the drying fluid to penetrate all surfaces of the solid articles to be dried. However, this heating has the effect of raising the temperature of the articles. The temperature differential between the ambient environment and the article after such heating can be as much as 15 to 20 degrees Fahrenheit even using the apparatus and method in accordance with the invention herein. If not controlled, condensation will form on the dried articles causing particulates and contaminates to form on the dried articles. By passing the dried articles through the intermediate step of the condensation prevention system 18, condensation is virtually eliminated.

The drying apparatus 10 includes a separation tank 20 for collecting the drying fluid once it has been sprayed on the article (s) to be dried. The separation tank 20 includes a separation filter 22 for separating the HFE from the remainder of the drying fluid. The drying fluid is mixed with de-ionized water (DI water).

Upon initial separation by the separation filter 22, the IPA/DI water is funneled to a waste tank 26. The HFE is then pumped by a pump 28 through a series of HFE filters 30. Upon secondary filtration, the HFE can be saved or recycled into the drying fluid supply system.

The drying apparatus 10 additionally includes a drying fluid supply system generally denoted by the numeral 100. The drying fluid supply system 100 includes a reservoir 102 having a supply of drying fluid connected by a supply line 104 to the spray member 14. An in- line heating unit 106 in supply line 104 and between the reservoir 102 and the spray member 14 heats the drying fluid to the desired temperature. Additionally, in other preferred embodiments, an in-line heating unit may be excluded or simply turned off and the drying fluid may be used unheated.

The exemplary embodiment of the drying fluid supply system 100 includes a spiking system generally denoted by the numeral 110. The spiking system 110 includes spike canisters 112 and 114 for each of the drying agent and the surfactant, respectively. Connection lines link the canisters 112 and 114 with various regulators and the reservoir 102. Additionally, the system 100 includes a spiking regulator for regulating the spiking of both the IPA and HFE. A series of valves, such as air operated or solenoid operated valves or like valves control the dispensing of the drying fluid and surfactant into the reservoir 102.

The spray member 14 includes a series of spray valves 15 as illustrated in Fig. 1. The spray valves 15 are connected for a series of pressure regulators 19 which are in turn connected to a series of valves and which are in turn connected to supply line 104.

In Use: In order to dry solid articles in accordance with the apparatus and method of the instant invention, the articles are inserted into the process tank 12 and fixing to the platform 16. Upon demand, the drying fluid is pressure forced from the reservoir 102 through the in-line heating unit 106 to one or more valves using a supply line 104. The in-line heating unit 106 heats the drying fluid before it is sprayed onto the articles.

After spraying the articles, the drying fluid together with any aqueous solution and contaminants, collects at the bottom of the process tank 12. At the bottom of the process tank 12, the collected fluid is removed through a drain 32. The collected fluid passes through a separation filter 34 and into the closed separation tank 20. The use of a closed separation tank 20 reduces evaporation of the carrier fluid in comparison to open tank separation vats in the prior art. The decrease in evaporation reduces environmental emissions associated with the

process. Additionally, the decrease in evaporation allows more of the HFE to be collected which decreases the costs of the drying operation dramatically since HFE is highly expensive.

The separation filter 34 filter creates surface tension between IPA, the aqueous solutions and contaminants and the HFE causing the aqueous solutions to separate from the drying fluid.

It will be noted as set forth above, that the IPA with aqueous solution (after spray drying) does not mix with the HFE. In one example, the separation filter 34 is made from a perforated material.

The process tank 12 includes connection to a waste tank 26 and a separation tank 20. The waste tank 26 which captures the overflow of IPA and other aqueous products (after spray drying). The IPA and other aqueous products may be further filtered through a series of filters (not shown) to filter out the contaminants and aqueous products in order to reuse the IPA.

A separation filter 34 is advantageously placed between the process tank 12 and the waste tank 26. It should be noted that the Residium and the alcohol with aqueous products (after spray drying) do not mix so that separation is encouraged based upon the selection of those chemical materials in conjunction with a thorough understanding of the method of drying in accordance with this invention. Additionally, the density difference between the Residium and alcohol with aqueous products causes the Residium to sink alone to the bottom of the separation tank and to be collected there for additional filtering. A pump pumps the separated Residium through a series of filters for cleaning any impurities and then back to the reservoir for re-use in the supply system drying agent composition.

The HFE is collected in the separation tank 20. The pump 28 forces the collected HFE through a series of HFE filters 30 for secondary filtration. These HFE filters 30 ready the HFE for recycling. Upon completion of the HFE secondary filtering process, the pump 28 pumps the filter the HFE back into the reservoir as desired.

The drying fluid supply system includes a concentration regulator for detecting and correcting spikes in the component concentrations of the drying fluid held in the reservoir 102.

In order to correct any variations, the concentration regulator dispenses components of the drying fluid from the component canisters 112,114 as desired into the reservoir 102. The concentration regulator is connected to a sample line, which extends into the drying fluid in the

reservoir 102. As noted above co icentrations of IPA higher than 6% can be used, but only when it does not cause the drying fluid to become flammable. As also noted above such flammability causes the drying fluid to go beyond preferred safety limitations.

Should the concentration of HFE to IPA become lower than a predetermined concentration, the regulator dispenses an appropriate amount of HFE from an HFE spike canister 112. If the concentration of HFE to IPA becomes higher than the predetermined concentration, the regulator dispenses an appropriate amount of IPA from an IPA spike canister 114. The regulator controls the dispensing of the components utilizing valves on lines extending from the spike canisters 112 and 114 to an inlet line into the reservoir 102.

In an alternative embodiment, the dryer does not include the reservoir 102 and the in-situ mixing of the HFE and IPA occurs using a supply line running between the HFE filters 30 and the in-line heating unit 106.

The valves control the dispensing of the drying fluid to the spray nozzles 15, which include in the preferred embodiment spray horns 36. The valves are independently pressure regulated and can be monitored by pressure regulators. The independent control of the valves allows each of the spray nozzles 15 to be adjusted for differing drying processes. For example, a first set of nozzles 15 may dispense a high pressure spray, a second set of nozzles 38 may dispense a moderate pressure spray, and a third set of spray nozzles 40 may dispense a mist or fog of drying fluid. After spraying, the process repeats as earlier described. In one embodiment, each set of spray nozzles 15,38 and 40 is actuated as the article moves through the process tank 12.

The material in the waste compartment 26 may also be filtered and recycled or simply discarded without great concern. The minimal amounts of contaminants and like products in the solution do not present an abnormal environmental hazard in the manufacturing process.

Thusly, the waste may be discarded without incurring great costs or difficult environmental procedures. Thusly, aqueous solutions and contaminants as well as the IPA collected in the waste compartment 26 are removed through a waste line.

Upon completion of the drying process, the dried articles are removed from the process tank. Where the articles were heated above ambient temperatures, it is preferred to pass the dried articles through the condensation prevention system 18 to prevent any possibility of the formation of condensation on the articles.

The cooling coils 24 are positioned above the spray nozzles 15 toward the top of the process tank 12 aid in collection by promoting condensation of the drying fluid spray. The

cooling coils 24 are secured within the process tank 12 and are cooled from a chilled water source external to the process tank 12.

In one embodiment, the pressure at which the drying fluid is spray is controlled to prevent and even limit reduce electrostatic discharge (ESD) from I psi to 120 psi.

The drying agent composition of this invention is comprised of a mixture of a hydrofluoroether and an alcohol with or without hydrofluoric acid. It is meant to be understood that the singular hydrofluoroether and the singular alcohol includes the plurals hydrofluoroethers and alcohols.

The drying agent composition in concert with the drying apparatus and method in accordance with this invention processes solid articles, including, but not limited to semiconductor wafers. The drying apparatus and method removes aqueous solutions from solid articles without adding static or electrostatically charged particulates or other contamination or stains. In one embodiment, the drying apparatus comprises a process tank and a drying agent composition supply system wherein the a drying agent composition is comprised of 0.1 % propyl alcohol and 99.9% methoxy nonafluorobutane. The process tank includes a spray member having multiple spray nozzles for spraying a non-flammable drying agent composition onto the surfaces of the article. In one embodiment the drying apparatus is top loading and in another embodiment the drying apparatus is front loading.

In another embodiment, the drying agent composition comprises a mixture of 1. 0% propylene glycol, 0.5% hydrofluoric acid and the balance, an azeotropic mixture of ethoxy nonafluorobutane and trans-2,1-dichloroethylene. The drying agent composition is non-VOC material, which leaves no residual residue on surfaces of the article after being sprayed on the article for drying. In another embodiment, the drying agent composition comprises 98.5% hydrofluoroether, 0.5% hydrofluoric acid and 1% of a equal mixture of isopropyl alcohol and propylene glycol. A pump ; compressed dry air supply, compressed nitrogen supply, or a gas may be used to force the drying agent composition through the spray nozzles.

In another embodiment, the drying agent composition comprises a mixture of 1.0% propylene glycol and the balance, an azeotropic mixture of ethoxy nonafluorobutane and trans- 2,1-dichloroethylene. The drying agent composition is non-VOC material, which leaves no residual residue on surfaces of the article after being sprayed on the article for drying. In another embodiment, the drying agent composition comprises 99.0% hydrofluoroether and 1% of a equal mixture of tertiary butyl alcohol and propylene glycol. A pump; compressed dry air supply, compressed nitrogen supply, or a gas may be used to force the drying agent composition through the spray nozzles.

Hydrofluoroethers useful in this invention are exemplified by CF3-CF2-CF2-CF2-0-CH3, methyl nonafluorobutyl ether and CF3-CF2-CF2-CF2-0-CF3, trifluoromethoxy nonafluorobutyl ether. Ethylated hydrofluoroethers are available from 3M Company as HFE-7100, HFE- 7100DL or HFE-7200 or as a mixture of hydrofluoroether or ethylated hydrofluoroethers with one or more chemicals, such as trans-1, 2-dichloroethylene, H2CIC-CCICH2 or other haloalkanes.

The hydrofluoroether has a chemical composition that is either CF3-CF2-CF2-CF2-0-CF3, or (CF3) 2-CF-CF2-O-CF3 or CF3-CF2-CF2-O-CF2-CF3 or (CF3) 2-CF-O-CF2-CF3 or generically as C 50FI2 or a mixture of these compositions. Other hydrofluoroethers contemplated by this invention include chemical compositions such as CF3-CF2-CF2-CF2-O-CF2-CF3 or CF3-CF2-CF2-CF2-CF2-O-CF3 or CF3-CF2-CF2-CF2-CH2-O-CF3 or CF3-CF2-CF2-CH2-CF2-O-CF3 or CF3-CF2-CH2-CF2-CF2-O-CF3 or CF3-CH2-CF2-CF2-CF2-O-CF3 or (CF3) 2-CF-CF2-CH2-O-CF3 or (CF3) 2-CF-CH2-CF2-O-CF3 or CF3-CF2-CF2-O-CF2-CH2-CF3 or CF3-CF2-CF2-O-CH2-CF2-CF3 or CF3-CF2-CH2-O-CF2-CF2-CF3 or CF3-CH2-CF2-O-CF2-CF2-CF3 or (CF3) 2-CF-O-CF2-CH2-CF3 or (CF3) 2-CF-O-CH2-CF2-CF3 or (CF3) 2-CF-CH2-O-CF2-CF3 or generically as C6H2OFs2 or a mixture of these compounds. Hydrofluoroethers and ethoxy hydrofluoroethers can be obtained from 3M Company in various formulations under the trade name Novec.

Alcohols useful in this invention include monohydric alcohols such as tertiary butyl alcohol, isopropyl alcohol and polyhydric alcohols such as propylene glycol, ethylene glycol, ethyloxylated propylene glycol and the like. Particularly useful are those alcohols that have

miscibility with water. It will be understood by one of ordinary skill in the art that the relative proportions of these compounds in a mixture may vary without deviating from the teaching of this invention.

Drying Fluid Embodiments: As noted above, the amount of IPA will greatly depend upon the mass of the articles inserted into the drying apparatus in a particular drying operation. In one embodiment, the mixture is 0.03% IPA and the remainder is HFE. In alternative embodiments, other mixtures in which IPA is within the range of 0.03% to 6.0% are used. Additionally, an isopropanol and hydrofluorocarbon (HFC)-based fluid, such as Vertrel X-P10, available from E. I du Pont de Nemours and Company, is used in other embodiments.

Drying Agent Composition Embodiments: As noted above, the amount of alcohol will greatly depend upon the desired drying time of the articles inserted into the drying apparatus in a particular drying operation. In one embodiment, the mixture is 0.03% alcohol and the remainder is hydrofluoroether. In alternative embodiments. other mixtures in which propylene glycol is within the range of 0.03% to 6.0% are used. Additionally, an isopropanol and hydrofluorocarbon (HFC)-based fluid, such as Vertrel X-PIO, available from E. I du Pont de Nemours and Company, is used in other embodiments.

While the foregoing detailed description has described several embodiments of the apparatus and method of drying solid articles in accordance with this invention, it is to be understood that the above description is illustrative only and not limiting of the disclosed invention. Particularly, while semiconductor wafers may have been discussed as the primary articles to be dried, the apparatus and method herein are not so limited. As noted above, the apparatus and method herein are primarily designed for solid articles. Additionally, while specific dimensions and mixtures have been disclosed, the invention herein is not so limited. It will be appreciated that the embodiments discussed above and the virtually infinite embodiments that are not described in detail are easily within the scope and spirit of this invention. Thus, the invention is to be limited only by the claims as set forth below.