Granted Patent B2

US 9,114,997 · App. 13/628,282 · Granted Aug 25, 2015

Abstract

Claims (56)

1. A process for depositing polycrystalline silicon on polycrystalline silicon particles by the thermal decomposition of silane in a fluidized bed reactor having a reaction chamber, the reaction chamber having a cross-section through which feed gases pass, the fluidized bed reactor producing at least about 100 kg/hr of polycrystalline silicon per square meter of reaction chamber cross-section, the process comprising introducing one or more feed gases into the reaction chamber with one or more of the feed gases comprising silane, the overall concentration of silane in the feed gases fed into the reaction chamber being less than about 15% by volume, the pressure in the reaction chamber being at least about 4 bar, and the average residence time of feed gases introduced into the reaction chamber is less than about 20 seconds; wherein silane thermally decomposes in the reaction chamber to deposit at least about 100 kg/hr of polycrystalline silicon per square meter of reaction chamber cross-section on the polycrystalline silicon particles.

2. The process as set forth in claim 1 wherein the temperature of all feed gases with a concentration of silane of at least about 1% is less than about 400° C. prior to entry into the reaction chamber.

3. The process as set forth in claim 1 wherein the pressure in the reaction chamber is at least about 10 bar.

4. The process as set forth in claim 1 wherein a spent gas is withdrawn from the fluidized bed reactor, the pressure of the spent gas being at least about 15 bar.

5. The process as set forth in claim 1 wherein particulate polycrystalline silicon is withdrawn from the fluidized bed reactor, the Sauter mean diameter of the particulate polycrystalline silicon being from about 600 μm to about 2000 μm.

6. The process as set forth in claim 1 wherein at least about 300 kg/hr of silicon deposits on the silicon particles per square meter of reaction chamber cross-section.

7. The process as set forth in claim 1 wherein the overall concentration of silane in feed gases introduced into the reaction chamber is less than about 8% by volume.

8. The process as set forth in claim 1 wherein the reaction chamber is not partitioned into separate portions.

9. The process as set forth in claim 1 wherein the fluidized bed reactor comprises an annular inner chamber formed between a reaction chamber wall and an outer shell, the process comprising maintaining a pressure in the annular inner chamber at least about 1.1 bar below the pressure within the reaction chamber.

10. The process as set forth in claim 1 wherein the reaction chamber is heated to at least about 600° C.

11. The process as set forth in claim 1 wherein no more than one feed gas is introduced into the reaction chamber.

12. The process as set forth in claim 1 wherein a first feed gas and second feed gas are introduced into the reaction chamber.

13. The process of claim 12 wherein:

the first feed gas comprises between about 5% and about 20% by volume silane, and the temperature of the first feed gas is less than about 350° C. prior to entry into the reaction chamber; and

the second feed gas comprises less than about 5% by volume silane, and the temperature of the second feed gas is between about 350° C. and about 600° C. prior to entry into the reaction chamber.

14. The process as set forth in claim 1 wherein particulate polycrystalline silicon is withdrawn from the fluidized bed reactor, the Sauter mean diameter of the particulate polycrystalline silicon being from about 800 μm to about 1300 μm.

15. The process as set forth in claim 1 wherein the pressure in the reaction chamber is at least about 20 bar.

16. A process for depositing polycrystalline silicon on polycrystalline silicon particles by the thermal decomposition of silane in a fluidized bed reactor having a reaction chamber, the reaction chamber having a core region, a peripheral region and a cross-section through which feed gases pass, the fluidized bed reactor producing at least about 100 kg/hr of polycrystalline silicon per square meter of reaction chamber cross-section, the process comprising:

introducing a first feed gas comprising silane into the core region of the reaction chamber, the reaction chamber containing silicon particles and the first feed gas containing less than about 20% by volume silane, wherein silane thermally decomposes in the reaction chamber to deposit at least about 100 kg/hr of polycrystalline silicon per square meter of reaction chamber cross-section on the polycrystalline silicon particles; and

introducing a second feed gas into the peripheral region of the reaction chamber, wherein the concentration of silane in the first feed gas exceeds the concentration in the second feed gas and the pressure in the reaction chamber is at least about 4 bar;

wherein the average residence time of feed gases introduced into the reaction chamber is less than about 20 seconds.

17. The process as set forth in claim 16 wherein the fluidized bed reactor comprises an annular wall and has a circular cross-section having a center and a radius R, wherein the core region extends from the center to at least about 0.6R and the peripheral region extends from the core region to the annular wall.

18. The process as set forth in claim 16 wherein the temperature of the first feed gas is less than about 400° C. prior to entry into the reaction chamber.

19. The process as set forth in claim 16 wherein the temperature of the second feed gas is less than about 400° C. prior to entry into the reaction chamber.

20. The process as set forth in claim 16 wherein the second feed gas comprises less than about 1% by volume silane and the temperature of the second feed gas is at least about 300° C. prior to entry into the reaction chamber.

21. The process as set forth in claim 16 wherein the pressure in the reaction chamber is at least about 10 bar.

22. The process as set forth in claim 16 wherein a spent gas is withdrawn from the fluidized bed reactor, the pressure of the spent gas being at least about 4 bar.

23. The process as set forth in claim 16 wherein the concentration by volume of silane in the first feed gas is at least about 50% greater than the concentration by volume of silane in the second feed gas.

24. The process as set forth in claim 16 wherein at least about 75% of the silane introduced into the fluidized bed reactor is introduced through the core region.

25. The process as set forth in claim 16 wherein particulate polycrystalline silicon is withdrawn from the fluidized bed reactor, the Sauter mean diameter of the particulate polycrystalline silicon being from about 600 μm to about 2000 μm.

26. The process as set forth in claim 16 wherein the average residence time of gas introduced into the reaction chamber is less than about 12 seconds.

27. The process as set forth in claim 16 wherein at least about 1000 kg/hr of silicon deposits on the silicon particles per square meter of reaction chamber cross-section.

28. The process as set forth in claim 16 wherein the second feed gas comprises less than about 1% by volume silane.

29. The process as set forth in claim 16 wherein the second feed gas consists essentially of compounds other than silane.

30. The process as set forth in claim 16 wherein the second feed gas consists essentially of one or more compounds selected from the group consisting of silicon tetrachloride, hydrogen, argon and helium.

31. The process as set forth in claim 16 wherein the first feed gas comprises less than about 15% by volume silane.

32. The process as set forth in claim 16 wherein the overall concentration of silane in feed gases introduced into the reaction chamber is less than about 8% by volume.

33. The process as set forth in claim 16 wherein the reaction chamber is not partitioned into separate portions.

34. The process as set forth in claim 16 wherein the fluidized bed reactor comprises an annular inner chamber formed between a reaction chamber wall and an outer shell, the process comprising maintaining a pressure in the annular inner chamber at least about 5 bar below the pressure within the reaction chamber.

35. The process as set forth in claim 16 wherein the reaction chamber is heated to at least about 500° C.

36. The process as set forth in claim 16 wherein the pressure in the reaction chamber is at least about 20 bar.

37. A process for depositing polycrystalline silicon on polycrystalline silicon particles by the thermal decomposition of silane in a fluidized bed reactor having a reaction chamber with a cross-section and a distributor for distributing gases into the reaction chamber, the fluidized bed reactor producing at least about 100 kg/hr of polycrystalline silicon per square meter of reaction chamber cross-section, the process comprising introducing one or more feed gases into the distributor to distribute the gases into the reaction chamber, the reaction chamber containing silicon particles and the temperature of each feed gas comprising at least about 1% by volume silane being less than about 400° C. prior to introduction into the distributor, the pressure in the reaction chamber being at least about 4 bar, and the average residence time of feed gases introduced into the reaction chamber is less than about 20 seconds, wherein silane thermally decomposes in the reaction chamber to deposit at least about 100 kg/hr of polycrystalline silicon per square meter of reaction chamber cross-section on the polycrystalline silicon particles.

38. The process as set forth in claim 37 wherein the temperature of each feed gas comprising at least about 1% by volume silane is less than about 300° C. prior to entry into the distributor.

39. The process as set forth in claim 37 wherein the pressure in the reaction chamber is at least about 10 bar.

40. The process as set forth in claim 37 wherein a spent gas is withdrawn from the fluidized bed reactor, the pressure of the spent gas being at least about 20 bar.

41. The process as set forth in claim 37 wherein particulate polycrystalline silicon is withdrawn from the fluidized bed reactor, the Sauter mean diameter of the particulate polycrystalline silicon being from about 600 μm to about 2000 μm.

42. The process as set forth in claim 41 wherein a first feed gas and second feed gas are introduced into the reaction chamber, and further wherein:

the first feed gas comprises between about 5% and about 20% by volume silane, and the temperature of the first feed gas is less than about 350° C. prior to entry into the reaction chamber; and

the second feed gas comprises less than about 5% by volume silane, and the temperature of the second feed gas is between about 350° C. and about 600° C. prior to entry into the reaction chamber.

43. The process as set forth in claim 37 wherein the average residence time of gas introduced into the reaction chamber is less than about less than about 4 seconds.

44. The process as set forth in claim 37 wherein at least about 2000 kg/hr of silicon deposits on the silicon particles per square meter of reaction chamber cross-section.

45. The process as set forth in claim 37 wherein the overall concentration of silane in feed gases introduced into the reaction chamber is less than about 15% by volume.

46. The process as set forth in claim 37 wherein the reaction chamber is not partitioned into separate portions.

47. The process as set forth in claim 37 wherein the fluidized bed reactor comprises an annular inner chamber formed between a reaction chamber wall and an outer shell, the process comprising maintaining a pressure in the annular inner chamber greater than about 1 bar below the pressure within the reaction chamber.

48. The process as set forth in claim 37 wherein the reaction chamber is heated to at least about 700° C.

49. The process as set forth in claim 37 wherein the pressure in the reaction chamber is at least about 20 bar.

Assignments (10)