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

• US 6,767,843 B2
• Filed: 10/01/2001
• Issued: 07/27/2004
• Est. Priority Date: 10/03/2000
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Das, Mrinal Kanti, Palmour, John W., Lipkin, Lori A.
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): Luk, Olivia T.
• Application Number:
  US09/968,391
• Publication Number:
  US 20020072247A1
• Time in Patent Office: 1,030 Days
• Field of Search: 438/758, 438/770, 438/244, 438/275, 438/285, 257/77
• US Class Current: 438/758
• CPC Class Codes: H01L 21/02323 introduction of oxygen
• CPC Class Codes: H01L 21/02337 treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 21/28008 Making conductor-insulator-semiconductor electrodes
• CPC Class Codes: H01L 21/3145 formed by deposition from a gas or vapour
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/66068 the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• 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 by oxidizing the silicon carbide layer in an N₂O environment. A predetermined temperature profile and/or a predetermined flow rate profile of N₂O are provided during the oxidation. The predetermined temperature profile and/or predetermined flow rate profile may be constant or variable and may include ramps to steady state conditions. The predetermined temperature profile and/or 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:

oxidizing a layer of silicon carbide in an environment comprising N₂O using a predetermined temperature profile which includes an oxidation temperature of at least about 1200°

C.; and

wherein the step of oxidizing a layer of silicon carbide in an environment comprising N₂O, further comprises oxidizing the layer of silicon carbide utilizing a flow rate profile of N₂O which includes a flow rate which provides an initial residence time of the N₂O of at least about 11 seconds.

2. The method according to claim 1, wherein the initial residence time is from about 11 seconds to about 33 seconds.

3. The method according to claim 2, wherein the initial residence time is from about 19 seconds to about 22 seconds.

4. The method according to claim 1, wherein a total residence time of the N₂O is from about 28 seconds to about 84 seconds.

5. The method according to claim 1, wherein a total residence time of the N₂O is from about 49 seconds to about 56 seconds.

6. The 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 6 SLM.

7. The method according to claim 1, wherein the flow rate profile provides a flow rate of from about 3.5 to about 4 Standard Liters per Minute.

8. The method according to claim 1, wherein the step of oxidizing the silicon carbide layer is followed by the step of annealing.

9. The method according to claim 8, wherein the step of annealing is carried in at least one of an environment comprising Ar, an environment comprising N₂ and/or a hydrogen containing environment.

10. The method according to claim 9, wherein the step of annealing is carried out for about one hour.

11. The 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 1.11 cm/s.

12. The method according to claim 11, wherein the predetermined flow rate provides a velocity of the N₂O of from about 0.65 cm/s to about 0.74 cm/s.

13. The method according to claim 1, wherein the step of oxidizing the silicon carbide layer comprises oxidizing the silicon carbide layer in an environment comprising N₂O including at least one of oxidizing agents and/or inert gases.

14. The method according to claim 13, wherein the oxidizing agents comprise at least one of steam and/or O₂.

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

17. The method according to claim 1, wherein the silicon carbide layer comprises a silicon carbide layer on a non-silicon carbide substrate.

18. The method according to claim 1, wherein the silicon carbide layer comprises a portion of a silicon carbide substrate.

19. The method according to claim 1, wherein the oxidation temperature is about 1300°

C.

20. The method according to claim 19, wherein the step of oxidizing the silicon carbide layer is followed by the step of annealing.

21. The method according to claim 20, wherein the step of annealing is carried in at least one of an environment comprising Ar, an environment comprising N₂ and/or a hydrogen containing environment.

22. The method according to claim 20, wherein the step of annealing is carried out for about one hour.

23. The method according to claim 19, wherein the step of oxidizing the silicon carbide layer comprises oxidizing the silicon carbide layer in an environment comprising N₂O including at least one of oxidizing agents and/or inert gases.

24. The method according to claim 23, wherein the oxidizing agents comprise at least one of steam and/or O₂.

25. The method according to claim 19, wherein the step of oxidizing the silicon carbide layer is followed by the step of annealing in an environment comprising N₂O at an anneal temperature of greater than about 1100°

C.

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

27. The method according to claim 19, wherein the silicon carbide layer comprises a silicon carbide layer on a non-silicon carbide substrate.

28. The method according to claim 19, wherein the silicon carbide layer comprises a portion of a silicon carbide substrate.

15. A method of fabricating a silicon carbide structure, comprising:

oxidizing a layer of silicon carbide in an environment comprising N₂O using a predetermined temperature profile which includes an oxidation temperature of at least about 1200°

C.; and

then

annealing the oxidized layer of silicon carbide in an environment comprising N₂O at an anneal temperature of greater than about 1100°

C.