Silicon carbide single crystal and a method for its production

• US 20050183657A1
• Filed: 10/15/2004
• Published: 08/25/2005
• Est. Priority Date: 04/15/2002
• Status: Active Grant

• Current Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Original Assignee: Sumitomo Metal Industries Limited (Nippon Steel Corporation)
• Inventors: Kamei, Kazuhito, Kusunoki, Kazuhiko, Munetoh, Shinji
• Granted Patent: US 7,520,930 B2
• Time in Patent Office: Days
• US Class Current: 117/2
• CPC Class Codes: C30B 11/00 Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method C30B13/00, C30B15/00, C30B17/00, C30B19/00 take precedence; under a protective fluid C30B27/00
• CPC Class Codes: C30B 29/36 Carbides

Abstract

A bulk silicon carbide single crystal of good crystalline quality which includes a minimized number of structural defects and is free from micropipe defects can be produced by crystal growth in a melt of an alloy comprising Si, C, and M (wherein M is either Mn or Ti) and having an atomic ratio between Si and M in which the value of x, when express as Si_1-xM_x, is 0.1≦×≦0.7 in the case where M is Mn or 0.1≦×≦0.25 in the case where M is Ti at a temperature of the melt which is below 2000° C. The C component is preferably supplied into the melt by dissolution of a graphite crucible which contains the melt such that the melt is free from undissolved C. One method of crystal growth is performed by cooling the melt after a seed substrate is immersed in the melt.

Claims

1. A bulk silicon carbide single crystal which is essentially free of any micropipe defects.

2. A method of producing a silicon carbide single crystal characterized by comprising the steps of:

immersing a seed substrate of silicon carbide in a melt of an alloy comprising Si, C, and M (wherein M is either Mn or Ti) and having an atomic ratio between Si and M in which the value of x, when expressed as Si_1-xM_x, is 0.1≦

×

≦

0.7 in the case where M is Mn or 0.1≦

×

≦

0.25 in the case where M is Ti, the melt being free from undissolved C; and

allowing a silicon carbide single crystal to grow on the seed substrate by supercooling of the alloy melt as a molten solution at least in the vicinity of the seed substrate so as to create a state which is supersaturated with SiC.

3. A method as claimed in claim 2 wherein the supercooling of the alloy melt is achieved by cooling the alloy melt.

4. A method as claimed in claim 3 wherein the alloy melt has a temperature which is in the range of at least 1650°

C. and at most 2000°

C. when the substrate is immersed therein and wherein the cooling is performed at rate of 1-6°

C./min.

5. A method as claimed in claim 3 wherein the growth of the silicon carbide single crystal on the substrate is continued by terminating the cooling of the alloy melt at a temperature which is higher than the solidus temperature of the alloy and subsequently performing supercooling repeatedly by repeated heating and cooling of the melt.

6. A method as claimed in claim 2 wherein the supercooling of the alloy melt is achieved by forming a temperature gradient in the alloy melt.

7. A method as claimed in claim 6 wherein the temperature gradient of the alloy melt is in the range of 5-100°

C./cm and wherein the temperature of the alloy melt in the vicinity of the substrate is at least 1450°

C. and at most 2000°

C.

8. A method as claimed in claim 4 wherein the temperature is in the range of 1650-1850°

C.

9. A method as claimed in claim 2 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.

10. A method as claimed in claim 7 where in the temperature is in the range of 1650-1850°

C.

11. A method as claimed in claim 3 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.

12. A method as claimed in claim 4 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.

13. A method as claimed in claim 5 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.

14. A method as claimed in claim 6 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.

15. A method as claimed in claim 7 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.

16. A method as claimed in claim 8 wherein the C in the alloy melt is supplied by dissolution of a carbonaceous crucible which contains the alloy melt.