Methods of forming SiC MOSFETs with high inversion layer mobility

• US 8,536,066 B2
• Filed: 05/10/2010
• Issued: 09/17/2013
• Est. Priority Date: 09/16/2005
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Das, Mrinal K., Hull, Brett, Krishnaswami, Sumi
• Primary Examiner(s): GHYKA, ALEXANDER G
• Application Number:
  US12/776,831
• Publication Number:
  US 20100221924A1
• Time in Patent Office: 1,226 Days
• Field of Search: 438/762, 438/765, 438/770
• US Class Current: 438/770
• CPC Class Codes: H01L 21/02236 group IV semiconductor
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• 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

Abstract

Methods of forming an oxide layer on silicon carbide include thermally growing an oxide layer on a layer of silicon carbide, and annealing the oxide layer in an environment containing NO at a temperature greater than 1175° C. The oxide layer may be annealed in NO in a silicon carbide tube that may be coated with silicon carbide. To form the oxide layer, a preliminary oxide layer may be thermally grown on a silicon carbide layer in dry O₂, and the preliminary oxide layer may be re-oxidized in wet O₂.

Claims

1. A method of forming an oxide layer on silicon carbide, comprising:

thermally growing an oxide layer in the presence of metallic impurities on a layer of silicon carbide in a silicon carbide tube;

flowing NO into the silicon carbide tube; and

annealing the oxide layer in an environment containing the NO at a temperature greater than 1300°

C. in the silicon carbide tube.

2. The method of claim 1, wherein annealing the oxide layer comprises annealing the oxide layer in an environment containing NO at a temperature between about 1200 1300°

C. and about 1600°

C.

3. The method of claim 1, wherein annealing the oxide layer comprises annealing the oxide layer for about 2 hours.

4. The method of claim 1, wherein the silicon carbide tube comprises a tube of silicon carbide having a silicon carbide coating thereon.

5. The method of claim 4, wherein the silicon carbide coating on the silicon carbide tube comprises a silicon carbide coating deposited by chemical vapor deposition on the silicon carbide tube.

6. The method of claim 1, wherein thermally growing the oxide comprises thermally growing the oxide in the presence of metallic impurities.

7. The method of claim 6, wherein thermally growing the oxide comprises thermally growing the oxide in the presence of alumina including the metallic impurities.

8. The method of claim 1, wherein thermally growing the oxide layer comprises thermally growing the oxide layer to a thickness of between about 500 Å

and 900 Å

.

9. The method of claim 1, wherein the silicon carbide layer comprises an epitaxial layer of 4H p-type silicon carbide having an off-axis orientation that is tilted at about 8°

from a (0001) plane.

10. The method of claim 1, wherein thermally growing the oxide layer comprises:

thermally growing a preliminary oxide layer on the silicon carbide layer in dry O₂ at a temperature of about 1200°

C.; and

re-oxidizing the preliminary oxide layer in wet O₂ at a temperature of about 950°

C.