Environmentally safe methods and apparatus for depositing and/or reclaiming a metal or semi-conductor material using sublimation

• US 5,366,764 A
• Filed: 06/15/1992
• Issued: 11/22/1994
• Est. Priority Date: 06/15/1992
• Status: Expired due to Fees

• Current Assignee: Mandar B. Sunthankar
• Original Assignee: Mandar B. Sunthankar
• Inventors: Sunthankar, Mandar B.
• Primary Examiner(s): PADGETT, MARIANNE L
• Application Number:
  US07/898,577
• Time in Patent Office: 890 Days
• Field of Search: 427/561, 427/562, 427/563, 427/564, 427/568, 427/569-580, 427/591-597, 427/248.1, 427/249, 427/250, 427/251, 427/252, 427/255, 427/255.1, 427/345
• US Class Current: 427/248.1
• CPC Class Codes: C23C 14/22 characterised by the process of coating
• CPC Class Codes: C23C 14/24 Vacuum evaporation
• CPC Class Codes: C23C 14/564 Means for minimising impurities in the coating chamber such as dust, moisture, residual gases

Abstract

This invention describes an environmentally and occupationally safer method and apparatus for coating and/or reclaiming materials in low pressure inert atmospheres. This invention is useful for coating a large number of irregularly shaped articles, such as industrial fasteners, tools and the like, with metals, semiconductor materials, composites, or alloys. The process related to this invention is also useful for coating parts in a rack or barrel type coating apparatus, as well as the continuous coating of parts which are fed through the path of material vapor streams. The processes and apparatus disclosed use sublimation techniques which allow almost unrestricted size, shape and placement of the depositing source. Heating sources serve to sublimate materials which can then be directed to the desired substrate for condensing. Additional heating sources may be provided to prevent vapors from condensing on chamber surfaces, or these heating sources may be used to periodically or continuously recover extraneously deposited material. In the reclamation mode, coated articles may be heated until sublimation of the coating occurs to allow the material to be reclaimed for safe disposal or reuse.

Claims

1. A method for depositing a material onto at least one substrate within a chamber comprising the steps of:

a. providing at least one substrate within said chamber;

b. providing at least one source material within said chamber

c. providing a secondary emission surface within said chamber;

d. heating said source material;

e. vaporizing said source material to create a vaporized source material;

f. depositing a portion of said vaporized source material on said secondary emission surface;

g. heating said secondary emission surface to a temperature at which re-vaporization of said originally vaporized source material occurs;

h. re-emitting said deposited source material from said secondary emission surface; and

i. depositing said re-emitted source material onto said substrate.

2. A method for depositing material as described in claim 1 wherein said step of heating said source material is to a temperature less than its melting temperature and further comprising the step of shaping said source material to accommodate a simultaneous, multidirectional deposition upon said substrate.

3. A method for depositing material as described in claim 1 or 2 wherein said step of providing at least one source material within said chamber comprises the step of providing at least two sources of material within said chamber and wherein said sources of material have divergent view angles with respect to said substrate.

4. A method for depositing material as described in claim 1 or 2 wherein

said secondary emission surface is positioned to receive at least a portion of said vaporized source material from said source material and to have a divergent view angle with respect to said substrate.

5. A method for depositing material as described in claim 1 wherein said substrate has a coating area which is exposed throughout a solid view angle and wherein said source material has a sublimation area which substantially covers said solid view angle.

6. A method for depositing material as described in claim 1 wherein said chamber has chamber walls and wherein said chamber walls are substantially covered by said source material.

7. A method for depositing material as described in claim 4 wherein said chamber has chamber walls and wherein said source material and said secondary emission surface substantially cover said chamber walls.

8. A method for depositing material as described in claim 2 wherein said substrate has a contoured coating area, wherein said source material has a sublimation area, and wherein said sublimation area and said contoured coating area have substantially duplicate structure.

9. A method for depositing material as described in claim 8 wherein said contoured coating area is cylindrically shaped and wherein said sublimation area is cylindrically shaped.

10. A method for depositing material as described in claim 4 wherein said substrate has a contoured coating area, wherein said secondary emission surface has an emission area, and wherein said emission area and said contoured coating area have substantially duplicate structure.

11. A method for depositing material as described in claim 1 wherein said substrate has a coating area, wherein said source material has a sublimation area, and wherein said sublimation area is larger than said coating area.

12. A method for depositing material as described in claim 1 wherein said substrate has a coating area, wherein said source material has a sublimation area, and wherein said sublimation area is at least twice the area of said coating area.

13. A method for depositing material as described in claim 1 wherein said chamber has a chamber] wall area and wherein said source material has a sublimation area, and wherein said sublimation area is at least as large as said chamber wall area.

14. A method for depositing material as described in claim 4 wherein said chamber has a chamber] wall area, wherein said source material has a sublimation area, wherein said secondary emission surface has an emission area, and wherein said sublimation area and said emission area are at least as large as said chamber wall area.

15. A method for depositing material as described in claim 4 wherein said source material has a sublimation area and wherein said secondary emission surface has an emission area and wherein said sublimation area is larger than said emission area.

16. A method for depositing material as described in claim 4 wherein said source material has a sublimation area and wherein said secondary emission surface has an emission area and wherein said emission area is larger than said sublimation area.

17. A method for depositing material as described in claim 1 and further comprising the step of maintaining said substrate stationary during said step of depositing.

18. A method for depositing material as described in claim 17 and further comprising the step of moving said source material during said step of depositing.

19. A method for depositing material as described in claim 17 and further comprising the step of maintaining said source material stationary during said step of depositing.

20. A method for depositing material as described in claim 4 and further comprising the step of moving said secondary emission surface during said step of depositing.

21. A method for depositing material as described in claim 19 wherein said substrate has a plurality of coating surfaces and wherein said step of depositing is achieved simultaneously for each coating surface.

22. A method for depositing a material onto at least one substrate within a chamber comprising the steps of:

a. providing at least one substrate within said chamber;

b. providing at least one solid source material within said chamber wherein said source material has a melting temperature;

c. providing at least one secondary emission surface within said chamber wherein said secondary emission surface is oriented toward said substrate;

d. establishing a pressure below atmospheric pressure within said chamber at which said source material efficiently sublimates;

e. heating said source material to a temperature less than its melting temperature;

f. sublimating said source material to create a vaporized source material;

g. depositing a portion of said vaporized source material on said secondary emission surface;

h. heating said secondary emission surface to a temperature at which re-vaporization of said originally vaporized source material occurs;

i. re-emitting said deposited source material from said secondary emission surface; and

j. depositing said re-emitted source material onto said substrate.

23. A method for depositing material as described in claim 22 wherein said secondary emission surface receives vaporized source material at a rate of accumulation and wherein said step of re-emitting said deposited source material from said secondary emission surface is at a rate of re-emission and further comprising the step of establishing said rate of re-emission as at least as great as said rate of accumulation.

24. A method for depositing material as described in claim 23 wherein said step of establishing said rate of emission as at least as great as said rate of accumulation comprises the step of controlling the temperature of said secondary emission surface.

25. A method for depositing material as described in claim 23 wherein said step of establishing said rate of emission as at least as great as said rate of accumulation comprises the step of orienting said secondary emission surface.

26. A method for depositing material as described in claim 24 wherein said temperature of said secondary source causes sublimation.

27. A method for depositing material as described in claim 22 and further comprising the step of orienting said source material and at least one of said secondary emission surfaces to achieve multidirectional deposition.

28. A method for depositing material as described in claim 22 wherein said substrate has a contoured coating area, wherein said source material has a sublimation area, and wherein said secondary emission surface has an emission area, and wherein said contoured coating area, said sublimation area, and said emission area are cylindrically shaped.