Process and apparatus for treating wafers with process fluids

• US 4,778,532 A
• Filed: 08/13/1985
• Issued: 10/18/1988
• Est. Priority Date: 06/24/1985
• Status: Expired due to Term

• Current Assignee: CFMT Inc.
• Original Assignee: CFM Technoligies Limited Partnership
• Inventors: Walter, Alan E., McConnell, Christopher F.
• Primary Examiner(s): Sneed, H. M. S.
• Assistant Examiner(s): Cohen, Sharon T.
• Application Number:
  US06/765,294
• Time in Patent Office: 1,162 Days
• Field of Search: 134/3, 134/10, 134/18, 134/25.1, 134/25.4, 134/26, 134/28, 134/29, 134/30, 134/31, 417/122, 417/118, 417/125, 210/739, 210/749, 210/750, 210/751, 210/758, 210/759, 210/760, 210/767
• US Class Current: 134/10
• CPC Class Codes: B05C 3/109 Passing liquids or other fluent materials into or through chambers containing stationary articles
• CPC Class Codes: B08B 2203/002 the liquid being a degassed liquid
• CPC Class Codes: B08B 3/04 Cleaning involving contact with liquid
• CPC Class Codes: B08B 7/0092 by cooling
• CPC Class Codes: C23C 16/54 Apparatus specially adapted for continuous coating
• CPC Class Codes: C30B 33/00 After-treatment of single crystals or homogeneous polycrystalline material with defined structure C30B31/00 takes precedence
• CPC Class Codes: H01L 21/67023 for general liquid treatment, e.g. etching followed by cleaning
• CPC Class Codes: H01L 21/67028 for cleaning followed by drying, rinsing, stripping, blasting or the like
• CPC Class Codes: H01L 21/67754 horizontal transfer of a batch of workpieces
• CPC Class Codes: H01L 21/67781 Batch transfer of wafers

Abstract

Contamination of wafers is reduced by an enclosed full-flow method and apparatus for the cleaning and other wet processing of semiconductor wafers. Process fluids flow sequentially and continuously past the wafers such that the processing does not require movement or operator handling of the wafers between processing steps. The vessel containing the wafers is hydraulically full during each process step. Wafers may be cleaned using a hot corrosive fluid, such as sulfuric acid; rinsed using high purity water at high flow rates; and dried using a drying fluid such an isopropanol. In addition, chemical reagents such as dilute hydrofluoric acid or hydrogen peroxide may be precisely mixed in situ and applied to the wafer surface for a precisely controlled period, by injecting concentrated reagent into rinse water purified by multipass filtration.

Claims

1. An enclosed, full flow method for the cleaning of semiconductor wafers comprising positioning said wafers in a vessel, closing said vessel to the environment, and flowing process fluids sequentially and continuously past said wafers in said vessel, including the steps of

(a) contacting said wafers with at least one cleaning fluid to remove contaminants from said wafers;

(b) removing said cleaning fluid from said wafers with a rinsing fluid; and

(c) removing said rinsing fluid from said wafers with a drying fluid;

whereby the processing does not requirement movement or operator handling of said wafers between said steps; and

maintaining the vessel containing said wafers hydraulically full during each process step.

2. A process according to claim 1 wherein process fluids are in continuous flow so that when any process fluid is not being used to contact said wafers, said non-contacting process fluid is continuously recirculated, such that the recirculation fluid flow paths do not include said vessel containing said wafers.

3. A process according to claim 1 wherein process fluids contact said wafers as a single fluid phase substantiaIly free of phase boundaries.

4. A method according to claim 1 comprising the additional steps of

(d) reacting the surface of said wafers with at least one chemical reagent and

(e) removing said chemical reagent from said wafers with a rinsing fluid.

5. A method according to claim 4 wherein said chemical reagent is followed by said rinsing fluid without an intervening fluid contacting said wafers.

6. A method according to claim 4 wherein said additional steps follow rinsing said cleaning fluid and precede removing said rinsing fluid with said drying fluid.

7. A method according to claim 1 wheren said wafers comprise a body selected from silicon and gallium arsenide.

8. A method according to claim 1 wherein said cleaning fluid comprises at least one acid selected from the group consisting of sulfuric acid and nitric acid.

9. A method according to claim 8 wherein said cleaning fluid additionally comprises an oxidizing agent selected from ozone and hydrogen peroxide.

10. A method according to claim 9 wherein said oxidizng agent is ozone and is injected into said acid as a gas whereby said gaseous ozone agitates said acid.

11. A method according to claim 8 wherein said acid is a hot, concentrated acid.

12. A method according to claim 1 wherein said cleaning fluid comprises at least one base.

13. A method according to claim 12 wherein said base is ammonium hydroxide.

14. A method according to claim 1 wherein said cleaning fluid is prefiltered through a particle filter which effectively removes particles having an average particle size greater than about 0.2 microns prior to contacting said wafers.

15. A method according to claim 1 wherein said cleaning fluid is recycled through said particle filter.

16. A method according to claim 15 wherein said particle filter is periodically backwashed to rejuvenate the filtration capability of said particle filter.

17. A process according to claim 1 wherein the flow of said cleaning fluid is effected by application of pressure to a surface of said cleaning fluid in a first storage reservoir, and said pressure effects the flow of cleaning fluid from said first storage reservoir, through a particle filter, into contact with said wafers, and subsequently to a second storage reservoir.

18. The process of claim 17 wherein the flow of fluid from first to second resevoir is reversed, wherein the direction of fluid flow through said particle filter and past said wafers is maintained.

19. A method according to claim 17 wherein said pressure application is effected by gas under pressure and said gas is a gas selected from nitrogen, argon, and compressed air.

20. A method according to claim 1 wherein said rinsing fluid is water.

21. A method according to claim 20 wherein said rinsing fluid is water which has been deionized and filtered to remove dissolved and suspended matter.

22. A method according to claim 21 wherein said water is continuously recirculated through cationic ion exchange resin and anionic ion exchange resin prior to use in rinsing wafers.

23. A method according to claim 22 wherein said water is continuously recirculated through at least one filtration membrane prior to use in rinsing wafers.

24. A method according to claim 23 wherein said filtration membrane is selected from micron filtration membranes, ultrafiltration membranes and reverse osmosis filtration membranes.

25. A method according to claim 20 wherein said water is irradiated and circulated to avoid bacterial growth.

26. A method according to claim 25 wherein the circulation of said water is by means of a vertical immersion pump.

27. A method according to claim 15 wherein filtration is effected by flow of said water through at least one filtration membrane which effectively removes particulate matter having an average particle size greater than 0.2 microns.

28. A method according to claim 23 wherein said filtration membrane is regenerated by periodically backwashing.

29. A method according to claim 1 wherein said wafers are rinsed at a fluid velocity of about 0.01 to 0.2 meters per second.

30. A method according to claim 1 where the effluent of said rinsing fluid is evaluated by measuring the electrical resistivity to sense the concentration of dissolved ions as a measure of fluid quality and the rinsing endpoint.

31. A method according to claim 1 wherein the effluent of said rinsing fluid is evaluated by measuring the population density of suspended particles as a measure of fluid quality and the rinsing endpoint.

32. A method according to claim 1 wherein said cleaning fluid is displaced by pressurized gas prior to rinsing step (b).

33. A method according to claim 32 wherein said cleaning fluid is allowed to drain by gravity from the surface of said wafers prior to said rinsing step (b).

34. A method according to claim 4 wherein said chemical reagent is an etchant.

35. A method according to claim 34 wherein said etchant is an aqueous solution of hydrofluoric acid.

36. A method according to claim 5 wherein said chemical reagent in concentrated form is diluted with said rinsing fluid to give diluted chemical reagent.

37. A method according to claim 36 wherein said chemical reagent in concentrated form is metered into said rinsing fluid at a predetermined rate after completion of rinsing step (b), wherein said rinsing fluid is deionized and filtered to give diluted chemical reagent which subsequently contacts said wafers.

38. A method according to claim 37 wherein said concentrated chemical reagent is injected into said rinsing fluid by valve means through which said chemial reagent is continuously recirculated when not being metered into said rinsing fluid.

39. The method of claim 38 wherein said valve has at least two flow paths within the body of said valve means such that while said chemical reagent is continuously recirculated through one of said flow paths rinsing fluid circulates through another of said flow paths.

40. A method according to claim 36 wherein said concentrated chemical reagent and said rinsing fluid are mixed by means of a static mixer prior to said chemical reagent contacting said wafers.

41. A method according to claim 38 wherein subsequent to completing injection of said concentrated reagent, a portion of the flow of said rinsing fluid is directed to flow through said valve means to rinse said valve means and to rinse associated fluid communication means, whereby the injection of concentrated reagent may be abruptly terminated.

42. A method according to claim 41 whereby said rinsing fluid is diverted by means of an orifice plate.

43. A method according to claim 1 wherein said drying fluid is miscible with said rinsing fluid and substantially nonreactive with the surface of said wafers.

44. A method according to claim 1 wherein said drying fluid is selected from organic compounds having a boiling point of less than about 140 degrees centigrade at atmospheric pressure.

45. A method according to claim 43 wherein said drying fluid is superheated steam.

46. A method according to claim 45 herein said super heated steam is diluted with a carrier gas selected from nitrogen, argon and dry air.

47. A method according to claim 44 wherien said drying fluid is an alcohol selected from isopropanol, methanol, 1-propanol, tert-butanol and mixtures thereof.

48. A method according to claim 47 wherein rinsed wafers are contacted with a stream of alcohol vapor as said rinsing fluid is displaced by said alcohol vapor.

49. A method according to claim 47 wherein said wafers have a temperature lower than said alcohol vapor and liquid alcohol consequently condenses on said wafers.

50. A method according to claim 48 wherein alcohol is evaporated from said wafers after said alcohol has substantially replaced the rinsing fluid on said wafers.

51. A method according to claim 50 wherein the evaporation of said alcohol is assisted by a stream of gas flowing past said wafers.

52. A method according to claim 51 wherein said alcohol and residual rinsing fluid are collected as an effluent from the vessel containing said wafers.

53. A method according to claim 52 wherein effluent alcohol is stripped from effluent water by passing a gas through effluent water/alcohol mixture.

54. An enclosed, full flow method for the treatment of semiconductor wafers comprising positioning said wafers in a vessel, closing said vessel to the environment, and flowing process fluids in sequential steps continuously past said wafers in said vessel, including the step of exposing the surface of said wafers to at least one cleaning fluid, whereby the processing does not require movement or handling of said wafers between said steps.

55. An enclosed, full flow method for the treatment of semiconductor wafers comprising positioning said wafers in a vessel, closing said vessel to the environment, and flowing process fluids in sequential steps continuously past said wafers in said vessel, including the step of reacting the surface of said wafers with at least one chemical reagent, whereby the processing does not require movement or handling of said wafers between said steps and maintaining the vessel containing said wafers hydraulically full during each process step.

56. A method according to claim 55 including the additional step of removing said chemical reagent with a rinsing fluid.

57. An enclosed, full flow method for the cleaning of semiconductor wafers comprising positioning said wafers in a vessel, closing said vessel to the environment, and flowing process fluids in sequential steps continuously past said wafers in said vessel, including the step of rinsing the surface of said wafers with at least one rinsing fluid whereby the processing does not require movement or handling of said wafers between process steps and maintaining said vessel containing said wafers hydraulically full during each process step.

58. An enclosed, full flow method for the treatment of semiconductor wafers comprising positioning said wafers in a vessel, closing said vessel to the environment, and flowing process fluids in sequential steps continuously past said wafers in said vessel, including the step of rinsing the surface of said wafers with at least one rinsing fluid and subsequently removing said rinsing fluid with a drying fluid whereby the processing does not require movement or handling of said wafers between process steps and maintaining the vessel containing said wafers is hydraulically full during each process step.