Vapor deposition apparatus and process for continuous deposition of a thin film layer on a substrate
View Patent ↗An apparatus and related process are provided for vapor deposition of a sublimated source material as a thin film on a photovoltaic (PV) module substrate. A receptacle is disposed within a vacuum head chamber and is configured for receipt of a source material. A heated distribution manifold is disposed below the receptacle and includes a plurality of passages defined therethrough. The receptacle is indirectly heated by the distribution manifold to a degree sufficient to sublimate source material within the receptacle. A molybdenum distribution plate is disposed below the distribution manifold and at a defined distance above a horizontal plane of a substrate conveyed through the apparatus. The molybdenum distribution plate includes a pattern of holes therethrough that further distribute the sublimated source material passing through the distribution manifold onto the upper surface of the underlying substrate. The molybdenum distribution plate includes greater than about 75% by weight molybdenum.
1. A process for vapor deposition of a sublimated source material to form thin film on a photovoltaic (PV) module substrate, the process comprising:
supplying source material to a receptacle within a deposition head;
indirectly heating the receptacle with a heat source member disposed below the receptacle to sublimate the source material;
directing the sublimated source material downwardly within the deposition head through the heat source member;
conveying individual substrates below the heat source member; and,
distributing the sublimated source material that passes through the heat source member onto an upper surface of the substrates via a molybdenum distribution plate posited between the upper surface of the substrate and the heat source member, wherein said molybdenum distribution plate comprises greater than about 75% by weight molybdenum.
2. The process as in claim 1 , wherein leading and trailing sections of the substrates in the direction of conveyance are exposed to generally the same vapor deposition conditions to achieve a desired substantially uniform thickness of the thin film layer on the upper surface of the substrates.
3. The process as in claim 1 , wherein said molybdenum distribution plate comprises greater than about 95% by weight molybdenum.
4. The process as in claim 1 , wherein said molybdenum distribution plate consists essentially of molybdenum.
5. The process as in claim 1 , wherein said molybdenum distribution plate consists of molybdenum.
6. The process as in claim 1 , wherein the substrates are continuously conveyed at a substantially constant linear conveyance rate during the vapor deposition process.
7. The process as in claim 1 , further comprising:
heating the individual substrates to a substrate temperature prior to conveying individual substrates below the heat source member.
8. The process as in claim 7 , wherein the substrate temperature is between about 550° C. and about 700° C.
9. The process as in claim 7 , wherein the substrate temperature is between about 600° C. and about 650° C.
10. The process as in claim 8 , further comprising:
heating the molybdenum deposition plate to a plate temperature prior to distributing the sublimated source material that passes through the heat source member onto the upper surface of the substrates via the molybdenum distribution plate.
11. The process as in claim 10 , wherein the plate temperature is above about 725° C.
12. The process as in claim 10 , wherein the plate temperature is from about 750° C. to about 900° C.
13. The process as in claim 10 , wherein the plate temperature is from about 800° C. to about 850° C.
14. The process as in claim 10 , wherein the source material comprises cadmium telluride.
15. The process as in claim 14 , wherein distributing the sublimated source material that passes through the heat source member onto the upper surface of the substrates via the molybdenum distribution plate forms a cadmium telluride layer on the upper surface that has a thickness between about 1 μm and 5 μm.
16. The process as in claim 1 , further comprising:
heating the individual substrates to a substrate temperature prior to conveying individual substrates below the heat source member; and
heating the molybdenum deposition plate to a plate temperature prior to distributing the sublimated source material that passes through the heat source member onto the upper surface of the substrates via the molybdenum distribution plate.
17. The process as in claim 16 , wherein the substrate temperature increases no more than about 75° C. during deposition within the vapor deposition apparatus 100 .
18. The process as in claim 16 , wherein the substrate temperature increases from about 10° C. to about 60° C. during deposition within the vapor deposition apparatus 100 .
19. The process as in claim 16 , wherein the substrate temperature increases no more than about 15% of its initial temperature entering the vapor deposition apparatus 100 prior to exiting the vapor deposition apparatus 100 .
20. The process as in claim 16 , wherein the substrate temperature increases from about 2% to about 10% of its initial temperature entering the vapor deposition apparatus 100 prior to exiting the vapor deposition apparatus 100 .