Gallium nitride materials and methods

• US 20020187356A1
• Filed: 07/02/2002
• Published: 12/12/2002
• Est. Priority Date: 12/14/2000
• Status: Active Grant

• Current Assignee: MACOM Technology Solutions Holdings, Inc.
• Original Assignee: Nitronex Corporation
• Inventors: Gehrke, Thomas, Piner, Edwin L., Linthicum, Kevin J., Weeks, T. Warren Jr.
• Granted Patent: US 6,617,060 B2
• Time in Patent Office: Days
• US Class Current: 428/446
• CPC Class Codes: C30B 23/02 Epitaxial-layer growth
• CPC Class Codes: C30B 23/025 characterised by the substrate
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 25/183 being provided with a buffer layer, e.g. a lattice matching layer
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 29/68 Crystals with laminate structure, e.g. "superlattices"
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/0245 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/0251 Graded layers
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02598 monocrystalline
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 29/04 : characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/045 : by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/0649 : Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/155 : Comprising only semiconductor materials H01L29/154 takes precedence
• CPC Class Codes: H01L 29/2003 : Nitride compounds
• CPC Class Codes: H01L 29/201 : including two or more compounds , e.g. alloys H01L29/2006 takes precedence
• CPC Class Codes: H01L 29/205 : in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/225 : in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/66462 : with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
• CPC Class Codes: H01L 29/7786 : with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
• CPC Class Codes: H01L 29/7787 : with wide bandgap charge-carrier supplying layer, e.g. direct single heterostructure MODFET
• CPC Class Codes: H01L 29/78 : with field effect produced by an insulated gate H01L29/7725, H01L29/775, H01L29/778 take precedence
• CPC Class Codes: H01L 33/0066 : with a substrate not being a III-V compound
• CPC Class Codes: H01L 33/007 : comprising nitride compounds
• CPC Class Codes: H01L 33/0075 : comprising nitride compounds
• CPC Class Codes: H01L 33/04 : with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/06 : within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/12 : with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/32 : containing nitrogen
• CPC Class Codes: Y10T 428/24942 : including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/26 : Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/265 : 1 mil or less

Abstract

The invention provides semiconductor materials including a gallium nitride material layer formed on a silicon substrate and methods to form the semiconductor materials. The semiconductor materials include a transition layer formed between the silicon substrate and the gallium nitride material layer. The transition layer is compositionally-graded to lower stresses in the gallium nitride material layer which can result from differences in thermal expansion rates between the gallium nitride material and the substrate. The lowering of stresses in the gallium nitride material layer reduces the tendency of cracks to form. Thus, the invention enables the production of semiconductor materials including gallium nitride material layers having few or no cracks. The semiconductor materials may be used in a number of microelectronic and optical applications.

Claims

1. A semiconductor material comprising:

a silicon substrate;

a compositionally-graded transition layer formed over the silicon substrate; and

a gallium nitride material layer formed over the transition layer.

2. The semiconductor material of claim 1, wherein the composition of the transition layer is graded continuously across the thickness of the layer.

3. The semiconductor material of claim 1, wherein the composition of the transition layer is graded discontinuously across the thickness of the layer.

4. The semiconductor material of claim 1, wherein the transition layer comprises an alloy of gallium nitride selected from the group consisting of Al_xIn_yGa_(1-x-y)N, In_yGa_(1-y)N, and Al_xGa_(1-x)N.

5. The semiconductor material of claim 4, wherein the concentration of gallium in the transition layer is graded.

6. The semiconductor material of claim 4, wherein x and/or y is varied from a first value at a back surface of the transition layer to a second value at a front surface of the transition layer, wherein the back surface is closer to the substrate than the front surface.

7. The semiconductor material of claim 6, wherein the sum of the value of x and the value of y at the back surface is greater than 0.4.

8. The semiconductor material of claim 6, wherein the sum of the value of x and the value of y at the back surface is greater than 0.8.

9. The semiconductor material of claim 6, wherein the transition layer comprises Al_xIn_(1-x)N at the back surface of the transition layer in contact with the silicon substrate.

10. The semiconductor material of claim 6, wherein the sum of the value of x and the value of y at the front surface is less than 0.3.

11. The semiconductor material of claim 6, wherein the transition layer comprises GaN at a front surface of the transition layer in contact with the gallium nitride material layer and is free of gallium at a back surface of the transition layer in contact with the substrate.

12. The semiconductor material of claim 4, wherein the transition layer comprises Al_xGa_(1-x)N.

13. The semiconductor material of claim 4, wherein the value of x decreases in a direction away from the silicon substrate.

14. The semiconductor material of claim 4, wherein the value of y remains constant across the transition layer.

15. The semiconductor material of claim 1, wherein the transition layer comprises a superlattice.

16. The semiconductor material of claim 15, wherein the superlattice includes a series of alternating Al_xIn_yGa_(1-x-y)N and Al_aIn_bGa_(1-a-b)N layers.

17. The semiconductor material of claim 16, wherein the of value of x, y, a, and b are constant across respective layers and the thickness of the respective layers is varied across the transition layer.

18. The semiconductor material of claim 1, wherein the transition layer has a thickness between about 0.03 micron and about 20 microns.

19. The semiconductor material of claim 1, wherein the gallium nitride material layer comprises GaN.

20. The semiconductor material of claim 1, wherein the gallium nitride material layer comprises Al_xIn_yGa_(1-x-y)N.

21. The semiconductor material of claim 1, wherein the gallium nitride material layer has a thickness of greater than 0.75 micron.

22. The semiconductor material of claim 1, wherein the semiconductor material forms a semiconductor device.

23. The semiconductor material of claim 22, wherein the semiconductor material forms an LED.

24. The semiconductor material of claim 22, wherein the semiconductor material forms a laser diode.

25. The semiconductor material of claim 22, wherein the semiconductor material forms a FET.

26. The semiconductor material of claim 1, wherein the gallium nitride material layer has a crack level of less than 0.005 μ

m/μ

m².

27. The semiconductor material of claim 1, wherein the gallium nitride material layer has a crack level of less than 0.001 μ

m/μ

m²

28. The semiconductor material of claim 1, wherein the gallium nitride material layer is substantially free of cracks.

29. The semiconductor material of claim 1, wherein the gallium nitride material layer is monocrystalline.

30. The semiconductor material of claim 1, wherein the silicon substrate has a thickness of greater than 250 micron.

31. The semiconductor material of claim 1, wherein the silicon substrate is textured.

32. The semiconductor material of claim 1, further comprising an intermediate layer formed over the silicon substrate and under the transition layer.

33. The semiconductor material of claim 1, wherein the intermediate layer has a constant composition.

34. The semiconductor material of claim 1, wherein the intermediate layer comprises an alloy of gallium nitride selected from the group consisting of Al_xIn_yGa_(1-x-y)N In_yGa_(1-y)N, and Al_xGa_(1-x)N.

35. The semiconductor material of claim 1, wherein the silicon substrate comprises a silicon wafer.

37. The semiconductor material of claim 36, wherein the gallium nitride material layer comprises GaN.

38. The semiconductor material of claim 36, wherein the gallium nitride material layer comprises an alloy of gallium nitride selected from the group consisting of Al_xIn_yGa_(1-x-y)N, In_yGa_(1-y)N, and Al_xGa_(1-x)N.

39. The semiconductor material of claim 36, wherein the gallium nitride material layer has a thickness of greater than 0.5 micron.

40. The semiconductor material of claim 36, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.

41. The semiconductor material of claim 36, wherein the gallium nitride material layer has a crack level of less than 0.001 μ

m/μ

m².

42. The semiconductor material of claim 36, wherein the gallium nitride material layer is substantially free of cracks.

43. The semiconductor material of claim 36, wherein the gallium nitride material layer is monocrystalline.

44. The semiconductor material of claim 36, wherein the silicon substrate comprises a silicon wafer.

46. The semiconductor structure of claim 45, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.

47. The semiconductor material of claim 45, wherein the silicon substrate comprises a silicon wafer.

48. The semiconductor structure of claim 45, wherein the semiconductor structure forms an LED.

49. The semiconductor structure of claim 45, wherein the semiconductor structure forms a laser diode.

50. The semiconductor structure of claim 45, wherein the semiconductor structure forms a FET.

51. The semiconductor structure of claim 45, wherein the gallium nitride material layer has a crack level of less than 0.005 μ

m/μ

m².

52. The semiconductor structure of claim 45, wherein the gallium nitride material layer has a crack level of less than 0.001 μ

m/μ

m².

53. The semiconductor structure of claim 45, wherein the gallium nitride material layer is substantially free of cracks.

36. A semiconductor material comprising:

a silicon substrate;

a gallium nitride material layer formed over the silicon substrate, the gallium nitride material layer having a crack level of less than 0.005 μ

m/μ

m².

45. A semiconductor structure comprising:

a silicon substrate; and

a gallium nitride material layer formed over the silicon substrate and having a thickness of greater than 0.5 micron,

wherein the semiconductor structure forms a semiconductor device.

54. A method of producing a semiconductor material comprising:

forming a compositionally-graded transition layer over a silicon substrate; and

forming a gallium nitride material layer over the transition layer.

55. The method of claim 54, wherein the composition of the transition layer is graded continuously across the thickness of the layer.

56. The method of claim 54, wherein the transition layer comprises an alloy of gallium nitride selected from the group consisting of Al_xIn_yGa_(1-x-y)N, In_yGa_(1-x-y)N, and Al_xGa_(1-x)N.

57. The method of claim 54, wherein the concentration of gallium in the transition layer is graded.

58. The method of claim 56, wherein the value of x decreases in a direction away from the silicon substrate.

59. The method of claim 56, wherein the transition layer comprises Al_xGa_(1-x)N.

60. The method of claim 54, wherein the transition layer comprises a superlattice including a series of alternating Al_xIn_yGa_(1-x-y)N/Al_aIn_bGa_(1-a-b)N layers.

61. The method of claim 54, wherein the gallium nitride material layer comprises GaN.

62. The method of claim 54, wherein the gallium nitride material layer comprises Al_xIn_yGa_(1-x-y)N.

63. The method of claim 54, further comprising processing the semiconductor material to form at least one semiconductor device.

64. The method of claim 54, wherein the gallium nitride material layer has a crack level of less than 0.005 μ

m/μ

m².

65. The method of claim 54, wherein the gallium nitride material layer has a crack level of less than 0.001 μ

m/μ

m².

66. The method of claim 54, wherein the gallium nitride material layer is substantially free of cracks.

67. The method of claim 54, wherein the gallium nitride material layer is monocrystalline.

68. The method of claim 54, further comprising forming an intermediate layer over the silicon substrate and under the transition layer.

70. The method of claim 69, wherein the gallium nitride material layer comprises GaN.

71. The method of claim 69, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.

72. The method of claim 69, wherein the gallium nitride material layer has a crack level of less than 0.001 μ

m/μ

m².

73. The method of claim 69, wherein the gallium nitride material layer is substantially free of cracks.

74. The method of claim 69, wherein the gallium nitride material layer is monocrystalline.

69. A method of producing a semiconductor material comprising:

forming a gallium nitride material layer formed over a silicon substrate, the gallium nitride material layer having a crack level of less than 0.005 μ

m/μ

m²

75. A method of forming a semiconductor structure comprising:

forming a semiconductor structure comprising a silicon substrate, and a gallium nitride material layer formed over the silicon substrate and having a thickness of greater than 0.5 micron.

76. The method of claim 75, wherein the gallium nitride material layer has a thickness of greater than 1.0 micron.

77. The method of claim 75, wherein the gallium nitride material layer has a thickness of greater than 2.0 microns.

78. The method of claim 75, wherein the semiconductor structure forms an LED.

79. The method of claim 75, wherein the semiconductor structure forms a laser diode.

80. The method of claim 75, wherein the semiconductor structure forms a FET.

81. The method of claim 75, wherein the gallium nitride material layer has a crack level of less than 0.005 μ

m/μ

m².

82. The method of claim 75, wherein the gallium nitride material layer has a crack level of less than 0.001 μ

m/μ

m².

83. The method of claim 75, wherein the gallium nitride material layer is substantially free of cracks.

84. A semiconductor material comprising:

a silicon (100) substrate; and

a gallium nitride material layer having a Wurtzite structure formed over the silicon substrate.

85. The semiconductor material of claim 84, further comprising a compositionally-graded transition layer formed between the silicon (100) substrate and the gallium nitride material layer.