Semiconductor substrate and method for producing semiconductor substrate

1. A semiconductor substrate comprising:

single crystal silicon;

a mask material disposed on a surface of the single crystal silicon, the mask material having an opening and being comprised of an oxide doped with boron, an amount of boron in the mask material being in a range of 1 to 4 wt %;

a silicon carbide film disposed on a portion of the single crystal silicon, the portion being in the opening; and

a single crystal silicon carbide film disposed so as to cover the silicon carbide film and the mask material,

the mask material having a viscosity of 10 5 Pa·S or more and 10 14.5 Pa·S or less at a temperature in a range of 950 to 1400° C.

2. A semiconductor substrate comprising:

single crystal silicon;

a silicon carbide film disposed on a surface of the single crystal silicon;

a mask material disposed on a surface of the silicon carbide film, the mask material having an opening and being comprised of an oxide doped with boron, an amount of boron in the mask material being in a range of 1 to 4 wt %; and

a single crystal silicon carbide film disposed so as to cover the silicon carbide film and the mask material,

the mask material having a viscosity of 10 5 Pa·S or more and 10 14.5 Pa·S or less at a temperature in a range of 950 to 1400° C.

3. The semiconductor substrate according to claim 1 , the mask material being a silicon oxide film that contains phosphorous, an amount of the phosphorous being in a range from 1 to 8 wt %.

4. A method for producing a semiconductor substrate, comprising:

forming a mask material on a surface of single crystal silicon, the mask material being comprised of an oxide doped with boron, an amount of boron in the mask material being in a range of 1 to 4 wt %;

forming an opening in the mask material, thereby exposing a portion of the single crystal silicon;

forming a silicon carbide film on the portion of the single crystal silicon; and

forming a single crystal silicon carbide film covering the silicon carbide film and the mask material by epitaxially growing single crystal silicon carbide in a temperature range of 950 to 1400° C. using the silicon carbide film as a starting point, wherein the mask material has a viscosity of 10 5 Pa·S or more and 10 14.5 Pa·S or less in a temperature range of 950 to 1400° C.

5. A method for producing a semiconductor substrate, comprising:

forming a silicon oxide film on a surface of single crystal silicon;

forming an opening in the silicon oxide film, thereby exposing a portion of the single crystal silicon;

forming a silicon carbide film on the portion of the single crystal silicon;

epitaxially growing single crystal silicon carbide using the silicon carbide film as a starting point and stopping the epitaxial growth of the single crystal silicon carbide in a state that a portion of the surface of the silicon oxide film is exposed;

forming a mask material by doping the silicon oxide film with boron, an amount of boron in the mask material being in a range of 1 to 4 wt %; and

forming a single crystal silicon carbide film covering the mask material in a temperature range of 950 to 1400° C. by restarting the epitaxial growth of the single crystal silicon carbide after the forming of the mask material, wherein

the mask material has a viscosity of 10 5 Pa·S or more and 10 14.5 Pa·S or less in a temperature range of 950 to 1400° C.

6. A method for producing a semiconductor substrate, comprising:

forming a silicon carbide film on a surface of single crystal silicon;

forming a mask material on a surface of the silicon carbide film, the mask material being comprised of an oxide doped with boron, an amount of boron in the mask material being in a range of 1 to 4 wt %;

forming an opening in the mask material, thereby exposing a portion of the silicon carbide film; and

forming a single crystal silicon carbide film covering the silicon carbide film and the mask material by epitaxially growing single crystal silicon carbide in a temperature range of 950 to 1400° C. using the portion of the silicon carbide film as a starting point, wherein the mask material has a viscosity of 10 5 Pa·S or more and 10 14.5 Pa·S or less in a temperature range of 950 to 1400° C.

7. A method for producing a semiconductor substrate, comprising:

forming a silicon carbide film on a surface of single crystal silicon;

forming a silicon oxide film on a surface of the silicon carbide film;

forming an opening in the silicon oxide film, thereby exposing a portion of the silicon carbide film;

epitaxially growing single crystal silicon carbide using the portion of the silicon carbide film as a starting point, and the epitaxial growth of the single crystal silicon carbide is stopped in a state that a portion of the surface of the silicon oxide film is exposed;

forming a mask material by doping the silicon oxide film with boron, an amount of boron in the mask material being in a range of 1 to 4 wt %; and

forming a single crystal silicon carbide film covering the mask material in a temperature range of 950 to 1400° C. by restarting the epitaxial growth of the single crystal silicon carbide after the forming of the mask material, wherein

the mask material has a viscosity of 10 5 Pa·S or more and 10 14.5 Pa·S or less in a temperature range of 950 to 1400° C.

8. The method for producing a semiconductor substrate according to claim 4 , wherein the mask material is formed of a silicon oxide film containing phosphorous in an amount ranging from 1 to 8 wt %.

9. The method for producing a semiconductor substrate according to claim 5 , wherein the forming of the mask material comprises:

forming an impurity-containing layer doped with an impurity and covering the silicon oxide film;

forming the mask material by diffusing the doped impurity in the impurity-containing layer into the silicon oxide film by heating the impurity-containing layer; and

removing the impurity-containing layer, thereby exposing the mask material.