Process for producing a single-crystal substrate of silicon carbide

Claim 2

A process for producing a single-crystal substrate of silicon carbide comprising growing a single-crystal film of α-silicon carbide on a single-crystal film of β-silicon carbide as a growth substrate.

Claim 3

A process according to claim 1, wherein said growth substrate is heated at a temperature in the range of 1,400° C. to 1,900° C.

Claim 4

A process according to claim 1, wherein a mixture of monosilane gas and propane gas is supplied as a source gas to the surface of said growth substrate with hydrogen gas as a carrier gas.

Claim 5

A process of producing a single-crystal substrate of silicon carbide comprising steps for: producing a single-crystal film of β-silicon carbide as a growth substrate by (1) covering the surface of a silicon substrate with a uniform thin film of β-silicon carbide grown by chemical vapor deposition at a temperature lower than the temperature for growing a β-silicon carbide single crystal, and (2) growing a single-crystal film of β-silicon carbide on the thin film by chemical vapor deposition at a higher temperature than in the preceding step, and growing a single-crystal film of α-silicon carbide on said single-crystal film of β-silicon carbide as a growth substrate.

Claim 6

A process of producing a single-crystal substrate of silicon carbide comprising steps for: producing a single-crystal film of β-silicon carbide as a growth substrate by (1) covering the surface of a silicon substrate with a uniform thin film of β-silicon carbide grown by chemical vapor deposition at a temperature lower than the temperature for growing a β-silicon carbide single crystal, and (2) growing a single-crystal film of β-silicon carbide on the thin film by chemical vapor deposition at a higher temperature than in the preceding step, and growing a single-crystal film of α-silicon carbide on said single-crystal film of β-silicon carbide as a growth substrate.

Claim 7

A process according to claim 4, wherein said low temperature is in the range of 800° C. to 1,200° C. and said higher temperature is in the range of 1,200° C. to 1,400° C., at atmospheric pressure.

Claim 8

A process according to claim 4, wherein said low temperature is in the range of 1,000° C. to 1,100° C. and said higher temperature is in the range of 1,300° C. to 1,350° C., at atmospheric pressure.

Claim 9

A process according to claim 4, wherein each of the two steps by the CVD method is conducted by supplying a mixture of silicon gas and carbon gas to the surface of the silicon substrate.

Claim 10

A process according to claim 7, wherein said silicon gas is one selected from the groups consisting of gases of SiH 4 , SiCl 4 , SiH 2 Cl 2 , (CH 3 ) 3 SiCl and (CH 3 ) 2 SiCl 2 , and said carbon gas is one selected from the groups consisting of gases of CCl 4 , CH 4 , C 3 H 8 and C 2 H 6 .

Claim 11

A process according to claim 7, wherein the mixing ratio of the mixture of the silicon gas and the carbon gas is 0.01 to 10 as the Si/C atomic number ratio.

Claim 12

A process according to claim 7, wherein said mixing ratio is in the range of 0.5 to 5.

Claim 13

A process according to claim 4, wherein said thin film of silicon carbide grown by the CVD method at a low temperature has a thickness in the range of 10 to 1,000 Å.

Claim 14

A process according to claim 4, wherein said thin film has a thickness in the range of 100 to 500 Å.

Claim 15

A process according to claim 4, wherein said single-crystal film of β-silicon carbide on the thin film has a thickness in the range of 0.1 to 50 μm.

Claim 16

A process according to claim 4, wherein said single-crystal film of β-silicon carbide has a thickness in the range of 0.5 to 5 μm or 10 to 50 μm.

Claim 17

A process according to claim 4, wherein each of the two steps by the CVD method is conducted by supplying a mixture of silicon gas, carbon gas, and a carrier gas to the surface of the silicon substrate.