Sequential lithographic methods to reduce stacking fault nucleation sites

• US 7,226,805 B2
• Filed: 06/22/2006
• Issued: 06/05/2007
• Est. Priority Date: 03/18/2004
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Lendenmann, Heinz, Sumakeris, Joseph John, Hallin, Christer
• Primary Examiner(s): Jackson; Jerome
• Assistant Examiner(s): Nguyen; Joseph
• Application Number:
  US11/425,954
• Publication Number:
  US 20060243985A1
• Time in Patent Office: 348 Days
• Field of Search: 438/105, 438/931, 257/628, 257/105, 257/627, 257/77, 257/E21.054, 257/E21.699
• US Class Current: 438/105
• CPC Class Codes: H01L 21/02378 Silicon carbide
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02529 Silicon carbide
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor

Abstract

An epitaxial silicon carbide layer is fabricated by forming first features in a surface of a silicon carbide substrate having an off-axis orientation toward a crystallographic direction. The first features include at least one sidewall that is orientated nonparallel (i.e., oblique or perpendicular) to the crystallographic direction. A first epitaxial silicon carbide layer is then grown on the surface of the silicon carbide substrate that includes first features therein. Second features are then formed in the first epitaxial layer. The second features include at least one sidewall that is oriented nonparallel to the crystallographic direction. A second epitaxial silicon carbide layer is then grown on the surface of the first epitaxial silicon carbide layer that includes the second features therein.

Claims

1. A method of fabricating an epitaxial silicon carbide layer comprising:

forming a plurality of first features in a surface of a silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction, the plurality of first features including at least one first sidewall that is oriented nonparallel to the predetermined crystallographic direction;

growing a first epitaxial silicon carbide layer on the surface of the silicon carbide substrate that includes the plurality of first features therein, the first epitaxial silicon carbide layer being thicker than a depth of the at least one first sidewall;

forming a plurality of second features in a surface of the first epitaxial layer, the plurality of second features including at least one second sidewall that is oriented nonparallel to the predetermined crystallographic direction; and

growing a second epitaxial silicon carbide layer on the surface of the first epitaxial layer that includes the plurality of second features therein, the second epitaxial silicon carbide layer being thicker than a depth of the at least one second sidewall.

2. A method according to claim 1 wherein forming a plurality of first features comprises:

masking the surface of the silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction; and

etching the surface of the silicon carbide substrate that is exposed by the masking to form the plurality of first features in the surface of a silicon carbide substrate that is masked.

3. A method according to claim 2 wherein etching comprises dry etching the surface of the silicon carbide substrate that is masked using NE₃ and/or SF₆.

4. A method according to claim 1 wherein the predetermined crystallographic direction is a <

11 20>

direction.

5. A method according to claim 1 wherein forming a plurality of first features comprises forming a plurality of trenches in the surface of the silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction, the plurality of trenches extending oblique and/or perpendicular to the predetermined crystallographic direction and including at least one first sidewall that is oriented nonparallel to the predetermined crystallographic direction.

6. A method according to claim 1 wherein forming a plurality of first features comprises forming a plurality of depressions in the surface of the silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction and including at least one first sidewall that is oriented nonparallel to the predetermined crystallographic direction.

7. A method according to claim 6 wherein the plurality of depressions comprises a periodically repeating pattern of hexagonal pits.

8. A method according to claim 1 wherein forming a plurality of second features comprises:

masking the surface of the first epitaxial layer; and

etching the surface of the first epitaxial layer that is exposed by the masking to form the plurality of second features in the first epitaxial layer that is masked.

9. A method according to claim 8 wherein etching comprises dry etching the first epitaxial layer that is masked using NF₃ and/or SF₆.

10. A method according to claim 1 wherein forming a plurality of second features comprises forming a plurality of trenches in the surface of the first epitaxial layer, the plurality of trenches extending oblique and/or perpendicular to the predetermined crystallographic direction and including at least one second sidewall that is oriented nonparallel to the predetermined crystallographic direction.

11. A method according to claim 1 wherein forming a plurality of second features comprises forming a plurality of depressions in the surface of the first epitaxial layer and including at least one second sidewall that is oriented nonparallel to the predetermined crystallographic direction.

12. A method according to claim 11 wherein the plurality of depressions comprises a periodically repeating pattern of hexagonal pits.

13. A method according to claim 1:

wherein growing the first epitaxial silicon carbide layer comprises growing the first epitaxial silicon carbide layer on the surface of the silicon carbide substrate that includes the plurality of first features therein such that the first epitaxial silicon carbide layer contains lower basal plane dislocation density than the silicon carbide substrate; and

wherein growing the second epitaxial silicon carbide layer comprises growing the second epitaxial silicon carbide layer on the surface of the first epitaxial silicon carbide layer that includes the plurality of second features therein such that the second epitaxial silicon carbide layer contains lower basal plane dislocation density than the first epitaxial silicon carbide layer.

14. A method according to claim 1 wherein the first and second features are laterally offset from one another.

15. A method according to claim 1 further comprising:

forming a bipolar device in the second epitaxial silicon carbide layer.

16. A method of fabricating an epitaxial monocrystalline layer comprising:

forming a plurality of first features in a surface of a monocrystalline substrate having an off-axis orientation toward a predetermined crystallographic direction, the plurality of first features including at least one first sidewall;

growing a first epitaxial layer on the surface of the monocrystalline substrate that includes the plurality of features therein, the first epitaxial layer being thicker than a depth of the at least one first sidewall;

forming a plurality of second features in a surface of the first epitaxial layer, the plurality of second features including at least one second sidewall; and

growing a second epitaxial layer on the surface of the first epitaxial layer that includes the plurality of second features therein, the second epitaxial layer being thicker than a depth of the at least one second sidewall.

17. A method according to claim 16 wherein forming a plurality of first features comprises:

masking the surface of the monocrystalline substrate having an off-axis orientation toward a predetermined crystallographic direction; and

etching the surface of the monocrystalline substrate that is masked to form the plurality of first features in the surface of a monocrystalline substrate that is masked.

18. A method according to claim 16 wherein forming a plurality of second features comprises:

masking the surface of the first epitaxial layer; and

etching the surface of the first epitaxial layer that is masked to form the plurality of second features in the surface of a first epitaxial layer that is masked.

19. A method according to claim 16:

wherein growing the first epitaxial layer comprises growing the first epitaxial layer on the surface of the monocrystalline substrate that includes the plurality of first features therein such that the first epitaxial layer contains lower basal plane dislocation density than the monocrystalline substrate; and

wherein growing the second epitaxial layer comprises growing the second carbide layer on the surface of the first layer that includes the plurality of second features therein such that the second epitaxial layer contains lower basal plane dislocation density than the first epitaxial layer.

20. A method according to claim 16 wherein the monocrystalline substrate comprises silicon carbide.

21. A method according to claim 16 wherein the first and second features are laterally offset from one another.

22. A method of fabricating an epitaxial silicon carbide layer comprising:

epitaxially growing from at least one first sidewall of a plurality of first features in a surface of a silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction to form a first epitaxial silicon carbide layer that is thicker than a depth of the at least one first sidewall, the at least one first sidewall being oriented nonparallel to the predetermined crystallographic direction; and

epitaxially growing at least one second sidewall of a plurality of second features in a surface of the first epitaxial layer to form a second epitaxial silicon carbide layer that is thicker than a depth of the at least one second sidewall, the at least one second sidewall being oriented nonparallel to the predetermined crystallographic direction.

23. A method according to claim 22 wherein the predetermined crystallographic direction is a <

11 20>

direction.

24. A method according to claim 22 wherein the plurality of first features comprises a plurality of trenches in the surface of the silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction, the plurality of trenches extending perpendicular to the predetermined crystallographic direction and including at least one first sidewall that is oriented nonparallel to the predetermined crystallographic direction.

25. A method according to claim 22 wherein the plurality of first features comprises a plurality of depressions in the surface of the silicon carbide substrate having an off-axis orientation toward a predetermined crystallographic direction, the plurality of depressions including at least one first sidewall that is oriented nonparallel to the predetermined crystallographic direction.

26. A method according to claim 25 wherein the plurality of depressions comprises a periodically repeating pattern of hexagonal pits.

27. A method according to claim 22 wherein the plurality of second features comprises a plurality of trenches in the surface of the first epitaxial layer, the plurality of trenches extending perpendicular to the predetermined crystallographic direction and including at least one second sidewall that is oriented nonparallel to the predetermined crystallographic direction.

28. A method according to claim 22 wherein the plurality of second features comprises a plurality of depressions in the surface of the first epitaxial layer, the plurality of depressions including at least one second sidewall that is oriented nonparallel to the predetermined crystallographic direction.

29. A method according to claim 28 wherein the plurality of depressions comprises a periodically repeating pattern of hexagonal pits.

30. A method according to claim 22 wherein the epitaxial silicon carbide layer contains lower basal plane dislocation density than the silicon carbide substrate.

31. A method according to claim 22:

wherein the first epitaxial silicon carbide layer contains lower basal plane dislocation density than the silicon carbide substrate; and

wherein the second epitaxial silicon carbide layer contains lower basal plane dislocation density than the first epitaxial silicon carbide layer.

32. A method according to claim 22 wherein the first and second features are laterally offset from one another.