Method for cleaning SiC monocrystal growth furnace

1. A method of cleaning a SiC monocrystal growth furnace using a gas to clean a SiC monocrystal growth furnace provided with an in-furnace substrate composed of a 3C—SiC polycrystal having at least a surface in which an intensity ratio of a (111) plane with respect to other crystal planes is at least 85% but not more than 100% according to powder XRD analysis, the method comprising:

flowing a mixed gas which consists of F 2 gas and an inert gas in a non-plasma state through an inside of the SiC monocrystal growth furnace, thereby selectively removing a SiC deposit deposited inside the SiC monocrystal growth furnace,

wherein the SiC deposit is a 3C—SiC polycrystal having an intensity ratio of the (111) plane with respect to the other crystal planes of less than 85% according to powder XRD analysis, and

wherein the mixed gas comprises at least 1 vol % but not more than 20 vol % of F 2 gas, and at least 80 vol % but not more than 99 vol % of the inert gas,

wherein a temperature of the inside the SiC monocrystal growth furnace is at least 200° C. but not more than 500° C., and

wherein the in-furnace substrate comprises an inner wall and members of the SiC monocrystal growth furnace.

2. The method of cleaning a SiC monocrystal growth furnace according to claim 1 , wherein a temperature inside the SiC monocrystal growth furnace is 280° C.-400° C.

3. The method of cleaning a SiC monocrystal growth furnace according to claim 1 , wherein the inert gas is selected from the group consisting of nitrogen gas, argon gas and helium gas.

4. A method of cleaning a SiC monocrystal growth furnace by using a gas to clean a SiC monocrystal growth furnace provided with an in-furnace substrate composed of a 3C—SiC polycrystal having at least a surface in which an intensity ratio of a (111) plane with respect to other crystal planes is at least 85% but not more than 100% according to powder XRD analysis, the method comprising:

flowing a mixed gas in a non-plasma state through an inside of the SiC monocrystal growth furnace, thereby selectively removing a SiC deposit deposited inside the SiC monocrystal growth furnace,

wherein the SiC deposit is a 3C—SiC polycrystal having an intensity ratio of the (111) plane with respect to the other crystal planes of less than 85% according to powder XRD analysis,

wherein the mixed gas comprises at least 1 vol % but not more than 20 vol % of F 2 gas, and at least 80 vol % but not more than 99 vol % of the inert gas, and a temperature of the inside the SiC monocrystal growth furnace is 280° C. 400° C.,

wherein the in-furnace substrate comprises an inner wall and members of the SiC monocrystal growth furnace, and

wherein the mixed gas consists of F 2 gas and an inert gas, or consists of F 2 gas, an inert gas and air.

5. The method of cleaning a SiC monocrystal growth furnace according to claim 4 , wherein the inert gas is nitrogen gas.

6. The method of cleaning a SiC monocrystal growth furnace according to claim 4 , wherein the inert gas is selected from the group consisting of nitrogen gas, argon gas and helium gas.

7. The method of cleaning a SiC monocrystal growth furnace according to claim 6 , wherein the inert gas is either nitrogen gas or argon gas.

8. A method of cleaning a SiC monocrystal growth furnace using a gas to clean a SiC monocrystal growth furnace provided with an in-furnace substrate composed of a 3C—SiC polycrystal having at least a surface in which an intensity ratio of a (111) plane with respect to other crystal planes is at least 85% but not more than 100% according to powder XRD analysis, the method comprising:

flowing a mixed gas which consists of F 2 gas and at least one of an inert gas and air in a non-plasma state through an inside of the SiC monocrystal growth furnace, thereby selectively removing a SiC deposit deposited inside the SiC monocrystal growth furnace, wherein the SiC deposit is a 3C—SiC polycrystal having an intensity ratio of the (111) plane with respect to the other crystal planes of less than 85% according to powder XRD analysis,

wherein the mixed gas comprises at least 1 vol % but not more than 20 vol % of F 2 gas, and at least 80 vol % but not more than 99 vol % of the inert gas, and a temperature of the inside the SiC monocrystal growth furnace is at least 200° C. but not more than 500° C., and

wherein the in-furnace substrate comprises an inner wall and members of the SiC monocrystal growth furnace.

9. The method of cleaning a SiC monocrystal growth furnace according to claim 8 , wherein a temperature inside the SiC monocrystal growth furnace is 280° C. 400° C.

10. The method of cleaning a SiC monocrystal growth furnace according to claim 8 , wherein the mixed gas consists of F 2 gas, the inert gas and the air.

11. The method of cleaning a SiC monocrystal growth furnace according to claim 8 , wherein the inert gas is nitrogen gas.

12. The method of cleaning a SiC monocrystal growth furnace according to claim 8 , wherein the mixed gas consists of F 2 gas and the inert gas, or consists of F 2 gas, the inert gas and the air.

13. The method of cleaning a SiC monocrystal growth furnace according to claim 8 , wherein the inert gas is selected from the group consisting of nitrogen gas, argon gas and helium gas.

14. The method of cleaning a SiC monocrystal growth furnace according to claim 13 , wherein the inert gas is either nitrogen gas or argon gas.