Seeded single crystal silicon carbide growth and resulting crystals

• US 20060213430A1
• Filed: 10/12/2005
• Published: 09/28/2006
• Est. Priority Date: 06/24/2002
• Status: Active Grant

• Current Assignee: Adrian Powell, Calvin H. Carter Jr, David Phillip Malta, George J. Jr. Fechko, Hudson Mcdonald Hobgood, Jason Ronald Jenny, Mark Brady, Robert Tyler Leonard, Stephan Georg Mueller, Valeri F. Tsvetkov
• Original Assignee: Adrian Powell, Calvin H. Carter Jr, David Phillip Malta, George J. Jr. Fechko, Hudson Mcdonald Hobgood, Jason Ronald Jenny, Mark Brady, Robert Tyler Leonard, Stephan Georg Mueller, Valeri F. Tsvetkov
• Inventors: Leonard, Robert Tyler, Powell, Adrian, Hobgood, Hudson McDonald, Brady, Mark, Malta, David Phillip, Jenny, Jason Ronald, Tsvetkov, Valeri F., Mueller, Stephan Georg, Carter, Calvin H. Jr., Fechko, George J. Jr.
• Granted Patent: US 7,316,747 B2
• Time in Patent Office: Days
• US Class Current: 117/109
• CPC Class Codes: C30B 23/00 Single-crystal growth by condensing evaporated or sublimed materials
• CPC Class Codes: C30B 23/025 characterised by the substrate
• CPC Class Codes: C30B 29/36 Carbides
• 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 21/324 Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering H01L21/20 - H01L21/288 and H01L21/302 - H01L21/322 take precedence

Abstract

A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system and in the absence of a solid silicon carbide source, by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.

Claims

1. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.

2. A method according to claim 1 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

3. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

conforming the seed holder-facing surface of the seed crystal and the shape of the seed-holder to one another by preventing any gap between the seed and the seed-holder from exceeding 10 μ

m.

4. A method according to claim 3 comprising preventing any gap between the seed and the seed-holder from exceeding 5 μ

m.

5. A method according to claim 3 comprising preventing any gap between the seed and the seed-holder from exceeding 2 μ

m.

6. A method according to claim 3 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

7. A method according to claim 3 comprising growing the bulk single crystal at substantially the same diameter as the seed crystal.

8. A method according to claim 3 wherein the step of conforming the seed and the seed holder comprises preparing a seed crystal with the seed holder-facing surface that is flat within 10 μ

m.

9. A method according to claim 3 wherein the step of conforming the seed and the seed holder comprises preparing a seed crystal with the seed holder-facing surface that is flat within 5 μ

m.

10. A method according to claim 3 wherein the step of conforming the seed and the seed holder comprises preparing a seed crystal with the seed holder-facing surface that is flat within 2 μ

m.

11. A method according to claim 3 wherein the step of conforming the seed and the seed holder comprises preparing a seed holder with a seed-facing surface that is flat within 10 μ

m.

12. A method according to claim 3 wherein the step of conforming the seed and the seed holder comprises preparing a seed holder with a seed-facing surface that is flat within 5 μ

m.

13. A method according to claim 3 wherein the step of conforming the seed and the seed holder comprises preparing a seed holder with a seed-facing surface that is flat within 2 μ

m.

14. A method according to claim 3 comprising lapping a seed crystal that is at least 2 inches in diameter.

15. A method according to claim 3 comprising lapping a seed crystal that is at least 100 mm in diameter.

16. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising lapping both sides of the seed crystal prior to growth.

17. A method according to claim 16 comprising lapping both sides of the seed crystal to surfaces that are flat within 10 μ

m.

18. A method according to claim 16 comprising lapping both sides of the seed crystal to surfaces that are flat within 5 μ

m.

19. A method according to claim 16 comprising lapping both sides of the seed crystal to surfaces that are flat within 2 μ

m.

20. A method according to claim 16 comprising:

lapping the seed crystal using an abrasive slurry in conjunction with a hard surface to quickly remove a fairly large amount of material; and

thereafter polishing the seed crystal to produce a finished surface of semiconductor material.

21. A method according to claim 16 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

22. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

maintaining a flat to slightly convex growth surface during the crystal growth while avoiding localized regions of undesired curvature within the first 10 mm of growth over the useable area of the crystal.

23. A method according to claim 22 comprising avoiding localized regions that show a concave surface shape within the first 10 mm of growth over the useable area of the crystal.

24. A method according to claim 22 comprising maintaining a flat to slightly convex growth surface during the first 500 μ

m of the crystal growth over the useable area of the crystal.

25. A method according to claim 22 comprising maintaining a flat to slightly convex growth surface with the convexity not exceeding a radius of curvature of 40 centimeters.

26. A method according to claim 22 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

27. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

separating the rear of the silicon carbide crystal from the seed holder by an amount sufficient for radiative heat transfer to dominate over conductive heat transfer between the seed and the seed holder.

28. A method according to claim 27 comprising maintaining a vacuum between the seed and seed-holder directly behind the seed.

29. A method according to claim 27 comprising maintaining a gas filled space between the seed and seed-holder directly behind the seed.

30. A method according to claim 27 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

31. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

growing the bulk single crystal from a seed crystal with a seed holder-facing surface that deviates from flat by no more than 10 microns.

32. A method according to claim 31 comprising growing the bulk single crystal from a seed crystal with a seed holder-facing surface that deviates from flat by no more than 5 microns.

33. A method according to claim 31 comprising growing the bulk single crystal from a seed crystal with a seed holder-facing surface that deviates from flat by no more than 2 microns.

34. A method according to claim 31 comprising growing the bulk single crystal from a seed crystal with a seed holder-facing surface that deviates from flat by no more than 1 micron.

35. A method according to claim 31 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

36. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

positioning the seed crystal for growth on a seed holder that deviates from flat by no more than 10 microns.

37. A method according to claim 36 comprising positioning the seed crystal for growth on a seed holder that deviates from flat by no more than 5 microns.

38. A method according to claim 36 comprising positioning the seed crystal for growth on a seed holder that deviates from flat by no more than 2 microns.

39. A method according to claim 36 comprising positioning the seed crystal for growth on a seed holder that deviates from flat by no more than 1 micron.

40. A method according to claim 36 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

41. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising growing the bulk single crystal on a seed crystal that is at least 1 millimeter thick.

43. A method according to claim 41 comprising growing the bulk single crystal on a seed crystal that is at least 1.4 millimeters thick.

45. A method according to claim 41 comprising growing the bulk crystal on a seed crystal of silicon carbide substrate that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

46. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

positioning the seed crystal in a crucible while exerting minimal torsional forces on the seed crystal to thereby prevent torsional forces from warping or bowing the seed crystal in a manner that that would otherwise encourage sublimation from the rear of the seed crystal or undesired thermal differences across the seed crystal.

47. A method according to claim 46 comprising mounting the seed crystal in an edge ring seed cap and positioning the edge ring seed cap on the seed holder to thereby minimize the mechanical forces applied to the seed crystal and thereby minimize or eliminate any distortion in the seed crystal resulting from its mounting on the seed holder.

48. A method according to claim 46 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

49. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

positioning a seed crystal on the seed holder with a low porosity backing material that provides a vapor barrier to silicon carbide sublimation from the seed and that minimizes the difference in thermal conductivity between the seed and the backing material to minimize or eliminate temperature differences across the seed and likewise minimize or eliminate vapor transport from the rear of the seed that would otherwise initiate and propagate defects in the growing crystal.

50. A method according to claim 49 comprising positioning the seed on the seed holder with a material that has a high carbon content, organic filler.

51. A method according to claim 49 comprising positioning the seed on the seed holder with a high temperature adhesive.

52. A seeded growth system according to claim 49 wherein said backing material has a coefficient of thermal expansion as close as possible to that of the SiC seed crystal.

53. A method according to claim 49 comprising positioning a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

54. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded growth system, and in the absence of a solid silicon carbide source, the improvement comprising:

annealing the seed holder prior to crystal growth to prevent the seed holder from significant distortion during crystal growth and thereby minimize or eliminate temperature differences across the seed that would otherwise tend to initiate and propagate defects in the growing crystal; and

thereafter initiating seeded growth with seed crystal.

55. A method according to claim 54 comprising growing the bulk single crystal at substantially the same diameter as the seed crystal.

56. A method according to claim 54 comprising initiating growth with a silicon carbide seed crystal that is at least 2 inches in diameter.

57. A method according to claim 54 comprising initiating growth with a silicon carbide seed crystal that is at least 100 mm in diameter.

58. A method according to claim 54 comprising annealing a seed holder at a temperature of at least about 2500°

C. for a period of at least about 30 minutes.

59. A method according to claim 54 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

60. In a method of producing a high quality bulk single crystal of silicon carbide in a seeded system, and in the absence of a solid silicon carbide source, the improvement comprising applying organic materials to a carbon seed-holder to improve the thermal uniformity of the seed holder under growth conditions.

61. A method according to claim 60 comprising applying a phenolic resin to the seed holder.

62. A method according to claim 60 comprising increasing the density of the seed holder using a mixture of an alcohol and a phenolic resin

63. A method according to claim 60 comprising increasing the density of the seed holder using a mixture of furfuryl alcohol and phenolic resin in a ratio of 2.5:

1.

64. A method according to claim 60 comprising matching the coefficient of thermal expansion of the seed holder to the coefficient of thermal expansion of the silicon carbide seed.

65. A method according to claim 60 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

71. In a seeded growth method for producing a high quality bulk single crystal of silicon carbide, and in the absence of a solid silicon carbide source, the improvement comprising selectively matching the coefficient of thermal expansion of the seed holder to the coefficient of thermal expansion of the silicon carbide seed.

72. A method according to claim 71 comprising matching a carbon seed holder to the silicon carbide seed material.

73. A method according to claim 71 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

74. In a seeded growth method for producing a high quality bulk single crystal of silicon carbide, and in the absence of a solid silicon carbide source, the improvement comprising positioning the seed on the seed holder with a high temperature adhesive.

75. A method according to claim 74 comprising positioning the seed on the seed holder with graphite glue.

76. A method according to claim 74 comprising initiating growth with a seed crystal of silicon carbide that has a polytype selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.