Silicon carbide substrate, semiconductor device, and methods for manufacturing them
A silicon carbide substrate capable of reducing on-resistance and improving yield of semiconductor devices is made of single-crystal silicon carbide, and sulfur atoms are present in one main surface at a ratio of not less than 60×10 10 atoms/cm 2 and not more than 2000×10 10 atoms/cm 2 , and oxygen atoms are present in the one main surface at a ratio of not less than 3 at % and not more than 30 at %.
1. A silicon carbide substrate in which a region including at least one main surface is made of single-crystal silicon carbide, the one main surface not being covered by any other semiconductor layer,
sulfur atoms being present in said one main surface at not less than 60×10 10 atoms/cm 2 and not more than 2000×10 10 atoms/cm 2 , and oxygen atoms being present in said one main surface at not less than 3 at % and not more than 30 at %.
2. The silicon carbide substrate according to claim 1 , wherein chlorine atoms are present in said one main surface at not more than 4000×10 10 atoms/cm 2 .
3. The silicon carbide substrate according to claim 1 , wherein carbon atoms are present in said one main surface at not less than 40 at % and not more than 60 at %.
4. The silicon carbide substrate according to claim 1 , wherein a metal impurity is present in said one main surface at not more than 11000×10 10 atoms/cm 2 .
5. The silicon carbide substrate according to claim 1 , wherein a metal impurity is present in said one main surface at not more than 4000×10 10 atoms/cm 2 .
6. The silicon carbide substrate according to claim 1 , wherein sodium atoms are present in said one main surface at not more than 10000×10 10 atoms/cm 2 .
7. The silicon carbide substrate according to claim 1 , wherein copper atoms and zinc atoms are present in said one main surface at a total of not more than 6000×10 10 atoms/cm 2 .
8. The silicon carbide substrate according to claim 1 , wherein said one main surface has a surface roughness of not more than 0.5 nm when evaluated in RMS.
9. The silicon carbide substrate according to claim 1 , having a diameter greater than 110 mm.
10. The silicon carbide substrate according to claim 1 , wherein
said single-crystal silicon carbide has a 4H structure, and
said one main surface has an off angle of not less than 0.1° and not more than 10° relative to a {0001} plane of said single-crystal silicon carbide.
11. The silicon carbide substrate according to claim 1 , wherein
said single-crystal silicon carbide has a 4H structure, and
said one main surface has an off angle of not less than 0.01° and not more than 6° relative to a (000-1) plane of said single-crystal silicon carbide.
12. The silicon carbide substrate according to claim 1 , wherein
said single-crystal silicon carbide has a 4H structure, and
said one main surface has an off angle of not more than 4° relative to a {03-38} plane of said single-crystal silicon carbide.
13. The silicon carbide substrate according to claim 1 , comprising:
a base layer; and
a single-crystal silicon carbide layer formed on said base layer,
wherein said one main surface is a surface of said single-crystal silicon carbide layer on a side opposite to a side facing said base layer.
14. A semiconductor device, comprising:
a silicon carbide substrate;
an epitaxial growth layer formed on one main surface of said silicon carbide substrate; and
an electrode formed on said epitaxial growth layer,
said silicon carbide substrate being a silicon carbide substrate as recited in claim 1 .
15. The semiconductor device according to claim 14 , further comprising a second electrode formed on the other main surface of said silicon carbide substrate as a main surface on a side opposite to a side facing said epitaxial growth layer.