Vacuum deposition methods and masking structure

• US 4,022,928 A
• Filed: 05/10/1976
• Issued: 05/10/1977
• Est. Priority Date: 05/22/1975
• Status: Expired due to Term

• Current Assignee: Bernhard P. Piwcyzk
• Original Assignee: Bernhard P. Piwcyzk
• Inventors: Piwcyzk, Bernhard P.
• Primary Examiner(s): Newsome, John H.
• Application Number:
  US05/684,563
• Time in Patent Office: 365 Days
• Field of Search: 106/2, 260/2 A, 427/43, 427/53, 427/154, 427/259, 427/264, 427/270, 427/271, 427/282, 427/99, 427/248 R, 427/248 H, 427/248 I, 427/248 J
• US Class Current: 430/296
• CPC Class Codes: C23C 14/042 using masks
• CPC Class Codes: C23C 14/12 Organic material
• CPC Class Codes: C23C 16/4404 Coatings or surface treatment on the inside of the reaction chamber or on parts thereof
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

A coating of a perfluoropolyether compound is applied to surfaces for inhibiting the deposition of a source material by evaporating or sputtering within a vacuum, and for the deposition of such material onto irregular surfaces, voids, or holes of an object. The coating can be applied by evaporating and then condensing the compound within a vacuum, or it can be applied as a fluid or thixotropic paste through direct contact by means such as a printing process. The coating can further be applied by spraying, or by spinning the surfaces about an axis with the fluid forming a thin coating through the action of centrifugal force. Selected portions of the coating can be removed so that the material is deposited in predetermined patterns. One method of removal is by dissolving the compound in a solvent. The coating can also be removed by selective evaporation in which a laser beam or an electron beam is directed across the surface. The beam evaporates the coating along a predetermined path whereby source material is subsequently condensed onto the substrate along this path. The vapor stream of material is reflected from surfaces coated with the compound so as to deposit onto surface portions of the object which are not in a line of sight with the source.

Claims

1. A method for inhibiting the deposition of a vapor stream of material onto surfaces within a vacuum, comprising applying a coating of perfluoropolyether onto surfaces upon which said deposition is to be inhibited.

2. A method as in claim 1 in which the coating is applied by placing said perfluoropolyether in fluid form within a vacuum chamber which encloses the surfaces, creating an inhibitor film forming vacuum within the chamber, and evaporating said fluid within the chamber to create a vapor stream therefrom which is deposited onto said surfaces within the chamber.

3. A method as in claim 2 in which said film formimg vacuum is established at a pressure in the range of about 10^-1 to 10^-7 Torr, and said fluid is heated to a temperature in the range of about 176°

to 600°

F for evaporating the same.

4. A method as in claim 1 in which the coating is applied by placing into a vacuum chamber one or more units of an open celled material absorbed with said perfluoropolyether in fluid form, and evaporating the fluid from the units into a vapor stream directed onto the surfaces.

5. A method as in claim 1 in which the coating is applied by evaporating perfluoropolyether into a vapor stream directed onto said surfaces.

6. a method as in claim 1 in which the coating is applied by placing the perfluoropolyether in fluid form onto the surfaces, spinning the surfaces about an axis, and forming the fluid by the action of centrifugal force in a thin film coating over the surfaces.

7. A method as in claim 1 in which the coating is applied by spraying perfluoropolyether onto selected surfaces.

8. A method as in claim 7 in which the coating is applied by spraying a solution of perfluoropolyether and a solvent onto the selected surfaces.

9. A method as in claim 8 in which said solvent is selected from the group consisting of perfluoro octane and trichlorotrifluorethane.

10. A method as in claim 1 in which said coating is applied by printing a solution of perfluoropolyether and a solvent onto selected surfaces in a pattern having area portions upon which said deposition is to be inhibited.

11. A method as in claim 1 comprising applying said perfluoropolyether across the surface of a substrate, and removing the coating over predetermined portions of the substrate whereby the vapor steam of material is subsequently deposited on said portions of the substrate surface

12. A method as in claim 11 in which the step of removing the coating is carried out by directing an electro-magnetic beam along a predetermined path whereby the coating is evaporated along the path.

13. A method as in claim 12 in which said beam comprises a laser beam.

14. A method as in claim 13 in which the wavelength of said laser beam is established within the infrared radiation energy absorption band of said perfluoropolyether.

15. A method as in claim 14 in which the wave number of said laser beam is established within the range of about 950 cm^-1 to 1450 cm^-1.

16. A method as in claim 12 in which said substrate surface reflects electromagnetic energy to minimize overheating of the surface and coating.

17. A method as in claim 12 in which said substrate surface is formed of a material which transmits electromagnetic energy to minimize overheating of the surface and coating.

18. A method as in claim 11 in which the step of removing the coating is carried out by directing an electron beam onto the coating along a predetermined path whereby the coating is evaporated along the path.

19. A method as in claim 1 in which said coating comprises a thixotropic mixture of perfluoropolyether and a viscous thickener.

20. A method as in claim 19 in which the thixotropic mixture is applied to selected surfaces by disposing a screen over the surfaces with portions of the screen having mesh openings coextensive with the selected surfaces, and the thixotropic mixture is applied over the screen and through the mesh openings onto the selected surfaces.

21. A method as in claim 19 in which the viscous thickener is selected from the group consisting of finely divided tetrafluoroethylene, finely divided alumina and silicon grease.

22. A method as in claim 1 in which said material is selected from the group consisting of a metal and carbon.

23. A method as in claim 22 in which the metal is selected from the group consisting of aluminum, gold, silver, copper, chromium, platinum, palladium, iron, lead, antimony, nickel and tin and alloys of these metals.

24. A method as in claim 11 in which the coating is removed by dissolving the perfluoropolyether in a solvent applied on the surface portions, and removing the dissolved perfluoropolyether from the surface portions.

25. A method for inhibiting the deposition of a vapor stream of material onto a viewing window within a vacuum chamber during a vapor deposition process, comprising applying a coating of perfluoropolyether onto the inner surface of said viewing window.

26. A masking structure for forming a body having a material which is condensed on the body into predetermined patterns from a vapor stream of the material within a vacuum, including the combination of a substrate having a surface, a masking layer covering predetermined areas of the substrate surface and other areas of the surface upon which said material is to be condensed being uncovered by said layer, said layer being formed of perfluoropolyether.

27. A masking structure as in claim 26 in which said body comprises a semiconductor body which includes said substrate.

28. A masking structure as in claim 26 in which the body includes a plurality of terminals, and at least certain of said other areas being arrayed in paths between selected terminals whereby material condensed along the paths forms electrical conductive paths.

29. A masking structure as in claim 26 in which said body comprises a lead frame having terminals and at least one semiconductor chip having contacts, and at least certain of said other area of the surface being arrayed in paths which extend between selected lead frame terminals and selected contacts.

30. In a vacuum deposition process, the method including the steps of forming a layer of perfluoropolyether onto selected portions of the surface of a substrate having other surface portions upon which material is to be deposited, creating a vacuum about said surface portions, forming said material into a vapor stream, and depositing said material from the vapor stream onto the other surface portions while said layer substantially inhibits the deposition of said material onto the selected surface portions.

31. In a process as in claim 30, wherein said first mentioned step includes forming a layer of perfluoropolyether having an average molecular weight within the range of substantially 1,170 to 6,700 onto the selected surface portions.

32. In a process as in claim 30, wherein said substrate surface includes the surface of a semiconductor body, and said first mentioned step includes forming a layer of said fluid onto the substrate surface and removing portions of the layer which overlie said selected surface portions.

33. In a process as in claim 30, wherein the substrate surface includes terminals and said step of removing the portions includes evaporating the layer along paths which lead between selected terminals.

34. In a process as in claim 33 wherein the substrate comprises a lead frame having terminals and at least one semiconductor chip having contacts, and said first mentioned step includes evaporating the layer along paths which extend between selected terminals and selected contacts.

35. In a process as in claim 30 wherein the substrate comprises a printed circuit board, and said first mentioned step includes forming said layer into a predetermined pattern over the surface with said other portions of the surface being uncovered by the layer whereby the material deposited on the other portions forms electrical conductive paths of a printed circuit.

36. A method for inhibiting the deposition of a vaporized material onto surfaces within a vacuum, comprising the step of forming on said surfaces a layer of a compound having the general formula:

##STR2## where x and n are integers.

37. A method as in claim 36 in which the compound has an average molecular weight within the range of 1,170 to 6,700.

38. A method as in claim 36 in which the layer is formed by evaporating the compound, and thereafter condensing the evaporated compound onto said surfaces.

39. A method as in claim 38 in which the evaporating step is carried out by heating the compound to above its distillation temperature in a gas selected from the group consisting of air, nitrogen, argon and helium, at a pressure of about one atmosphere.

40. A method as in claim 38 in which the evaporating step is carried out by heating the compound to a temperature in the range of about 176°

F to 600°

F at a pressure level below one atmosphere.

41. In a process for the vapor deposition of a source material onto an object, the steps of applying a coating of perfluoropolyether onto a surface which is positioned adjacent the object, forming the source material into a vapor stream in a vacuum which surrounds the object, and reflecting portions of the vapor stream from the surface toward the object for deposit thereon.

42. A process as in claim 41 in which the surface comprises at least a portion of the inner surface of the wall of a vacuum chamber or bell jar which is disposed about the object.

43. A process as in claim 41 in which the object includes surface portions not directly exposed on a line of sight with the source, and reflected portions of the vapor stream are deposited on said surface portions of the object.

44. A process as in claim 43 in which the object includes at least one through hole, and reflected portions of the vapor stream are deposited on the surfaces of the through hole.

45. A process as in claim 44 in which the object comprises a substrate having electronic device means, a masking structure is disposed over the substrate exposing the through holes, and the reflected portions of the vapor stream are directed through the masking structure and deposited on the through holes to form conductive paths with the electronic device means.

46. A process as in claim 44 in which the object is formed of a material which is not readily wettable with solder, the source material comprises a metal which is bonded by vapor deposition onto the surfaces of the through hole, and thereafter solder is bonded onto the deposited metal to form an electrical conductive path along the through hole.

47. A process as in claim 41 in which the object comprises a semiconductor substrate having surface portions covered by at least one layer of a material, with the layer having edges which slope toward or are normal with the substrate, and the vapor stream is deposited over the layer and substrate with reflected portions of the vapor stream being deposited along the edges of the layer.

48. A process as in claim 41 in which the object comprises a biological specimen having irregular surfaces or voids for use in electron microscope examination, and the material is deposited on the specimen with reflected portions of the vapor stream being deposited on the irregular surfaces or voids whereby the surface topography of the specimen is preserved.