Method of N2O annealing an oxide layer on a silicon carbide layer

• US 6,610,366 B2
• Filed: 04/12/2001
• Issued: 08/26/2003
• Est. Priority Date: 10/03/2000
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Lipkin, Lori A.
• Primary Examiner(s): BARR, MICHAEL E
• Application Number:
  US09/834,283
• Publication Number:
  US 20020172774A1
• Time in Patent Office: 866 Days
• Field of Search: 427/376.2, 427/377, 427/378, 427/126.3, 427/255.27, 438/787
• US Class Current: 427/378
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7827 Vertical transistors H01L29/7802, H01L29/78642 take precedence
• CPC Class Codes: H01L 29/7838 without inversion channel, e.g. buried channel lateral MISFETs, normally-on lateral MISFETs, depletion-mode lateral MISFETs

Abstract

Methods for fabricating a layer of oxide on a silicon carbide layer are provided by forming the oxide layer on the silicon carbide layer and then annealing the oxide layer in an N₂O environment at a predetermined temperature profile and at a predetermined flow rate profile of N₂O. The predetermined temperature profile and the predetermined flow rate profile are selected so as to reduce interface states of the oxide/silicon carbide interface with energies near the conduction band of SiC.

Claims

1. A method of fabricating a silicon carbide structure, comprising;

forming an oxide layer on a silicon carbide layer; and

annealing the oxide layer in an N₂O environment using a predetermined temperature profile which includes an anneal temperature of greater than 1100°

C. and a flow rate profile which includes a flow rate which provides an initial residence time of the N₂O of at least about 11 seconds.

2. A method according to claim 1, wherein the initial residence time is from about 11 seconds to about 45 seconds.

3. A method according to claim 1, wherein the initial residence time is from about 26 seconds to about 31 seconds.

4. A method according to claim 2, wherein a total residence time of the N₂O is from about 28 seconds to about 112 seconds.

5. A method according to claim 3, wherein a total residence time of the N₂O is from about 41 seconds to about 73 seconds.

6. A method according to claim 1, wherein the anneal temperature is at least about 1175°

C.

7. A method according to claim 6, wherein the anneal temperature is about 1200°

C.

8. A method according to claim 1, wherein the flow rate profile provides a flow rate of from about 2 Standard Liters per Minute (SLM) to about 8 SLM.

9. A method according to claim 1, wherein the flow rate profile provides a flow rate of from about 3 to about 5 Standard Liters per Minute.

11. A method according to claim 1, wherein the step of annealing the oxide layer is carried out for about 1.5 hours.

14. A method according to claim 1, wherein the predetermined flow rate provides a velocity of the N₂O of from about 0.37 cm/s to about 1.46 cm/s.

15. A method according to claim 14, wherein the predetermined flow rate provides a velocity of the N₂O of from about 0.5 cm/s to about 1 cm/s.

16. A method according to claim 1, wherein the step of forming the oxide layer comprises the step of depositing the oxide layer.

17. A method according to claim 1, wherein the step of forming the oxide layer comprises the step of thermally growing the oxide layer.

18. A method according to claim 1, wherein the step of forming the oxide layer further comprises performing a wet reoxidation of the oxide layer.

19. A method according to claim 1, wherein the silicon carbide layer comprises 4H polytype silicon carbide.

10. A method of fabricating a silicon carbide structure, comprising;

forming an oxide layer on a silicon carbide layer;

annealing the oxide layer in an N₂O environment using a predetermined temperature profile which includes an anneal temperature of greater than about 1100°

C. and a flow rate profile which includes a flow rate which provides an initial residence time of the N₂O of at least about 11 seconds; and

wherein the step of annealing the oxide layer is carried out for about 3 hours.

12. A method of fabricating a silicon carbide structure, comprising;

forming an oxide layer on a silicon carbide layer;

annealing the oxide layer in an N₂O environment using a predetermined temperature profile which includes an anneal temperature of greater than about 1100°

C. and a flow rate profile which includes a flow rate which provides an initial residence time of the N₂O of at least about 11 seconds; and

wherein the step of annealing the oxide layer is followed by the step of annealing the oxide layer in at least one of Ar and N₂.

13. A method according to claim 12, wherein the step of annealing the oxide layer in at least one of Ar and N₂ is carried out for about one hour.

20. A method of fabricating a silicon carbide structure, comprising;

forming an oxide layer on a silicon carbide layer; and

annealing the oxide layer in an N₂O environment using a predetermined temperature profile including an anneal temperature of greater than 1100°

C. and at a predetermined flow rate profile of N₂O, wherein the predetermined temperature profile and the predetermined flow rate profile are selected so as to reduce interface states of the oxide/silicon carbide interface with energies near the conduction band of SiC.

21. A method according to claim 20, wherein the anneal temperature is greater than about 1175°

C.

22. A method according to claim 21, wherein the anneal temperature is about 1200°

C.

23. A method according to claim 20, wherein the predetermined flow rate profile provides a flow rate of from about 2 Standard Liters per Minute (SLM) to about 8 SLM.

24. A method according to claim 23, wherein the flow rate is from about 3 to about 5 Standard Liters per Minute.

26. A method according to claim 20, wherein the step of annealing the oxide layer is carried out for about 1.5 hours.

29. A method according to claim 20, wherein the predetermined flow rate profile provides a velocity of the N₂O of from about 0.37 cm/s to about 1.46 cm/s.

30. A method according to claim 29, wherein the predetermined flow rate profile provides a velocity of the N₂O of from about 0.5 cm/s to about 1 cm/s.

31. A method according to claim 20, wherein the step of forming the oxide layer comprises the step of depositing the oxide layer.

32. A method according to claim 20, wherein the step of forming the oxide layer comprises the step of thermally growing the oxide layer.

33. A method according to claim 20, wherein the step of forming the oxide layer further comprises performing a wet reoxidation of the oxide layer.

34. A method according to claim 20, wherein the silicon carbide layer comprises a 4H polytype silicon carbide layer.

25. A method of fabricating a silicon carbide structure, comprising;

forming an oxide layer on a silicon carbide layer;

annealing the oxide layer in an N₂O environment using a predetermined temperature profile and at a predetermined flow rate profile of N₂O, wherein the predetermined temperature profile and the predetermined flow rate profile are selected so as to reduce interface states of the oxide/silicon carbide interface with energies near the conduction band of SiC; and

wherein the step of annealing the oxide layer is carried out for about 3 hours.

27. A method of fabricating a silicon carbide structure, comprising;

forming an oxide layer on a silicon carbide layer;

annealing the oxide layer in an N₂O environment using a predetermined temperature profile and at a predetermined flow rate profile of N₂O, wherein the predetermined temperature profile and the predetermined flow rate profile are selected so as to reduce interface states of the oxide/silicon carbide interface with energies near the conduction band of SiC; and

then

annealing the oxide layer in at least one of Ar and N₂.

28. A method according to claim 27, wherein the step of annealing the oxide layer in at least one of Ar and N₂is carried out for about one hour.