Silicon carbide substrate, silicon carbide semiconductor device, and methods for manufacturing silicon carbide substrate and silicon carbide semiconductor device

1. A method for manufacturing a silicon carbide substrate comprising steps of:

preparing a silicon carbide single crystal substrate having a first main surface, a second main surface, and a first side end portion, said second main surface being opposite to said first main surface, said first side end portion connecting said first main surface and said second main surface to each other, said first main surface having a width with a maximum value of more than 100 mm;

forming a silicon carbide epitaxial layer in contact with said first side end portion, said first main surface, and a boundary between said first main surface and said first side end portion; and

removing said silicon carbide epitaxial layer formed in contact with said first side end portion and said boundary, and

in the step of forming said silicon carbide epitaxial layer, said silicon carbide epitaxial layer is formed to have a stepped portion on said boundary, and

in the step of removing said silicon carbide epitaxial layer, said stepped portion is removed.

2. The method for manufacturing the silicon carbide substrate according to claim 1 , wherein

said stepped portion is formed to extend along a straight line obtained by rotating, in said first main surface in a range of ±20°, a straight line obtained by projecting a straight line parallel to a <11-20> direction onto said first main surface.

3. The method for manufacturing the silicon carbide substrate according to claim 1 , wherein said stepped portion has a length of not less than 50 μm and not more than 5000 μm in a direction from said first side end portion toward said center.

4. The method for manufacturing the silicon carbide substrate according to claim 1 , wherein said stepped portion has a depth of not less than 1 μm and not more than 50 μm in a direction perpendicular to said first main surface.

5. The method for manufacturing the silicon carbide substrate according to claim 1 , wherein said silicon carbide epitaxial layer has a thickness of not less than 5 μm on a center of said first main surface.

6. A method for manufacturing a silicon carbide semiconductor device, comprising steps of:

preparing the silicon carbide substrate manufactured by the method recited in claim 1 ; and

forming a silicon dioxide layer disposed to face a main surface of said silicon carbide epitaxial layer.

7. The method for manufacturing the silicon carbide semiconductor device according to claim 6 , wherein said silicon dioxide layer includes an ion implantation mask.

8. The method for manufacturing the silicon carbide semiconductor device according to claim 7 , wherein said ion implantation mask is in contact with said first side end portion of said silicon carbide single crystal substrate.

9. The method for manufacturing the silicon carbide semiconductor device according to claim 6 , wherein said silicon dioxide layer includes an interlayer insulating film.

10. The method for manufacturing the silicon carbide semiconductor device according to claim 6 , wherein said silicon dioxide layer has a thickness of not less than 0.8 μm and not more than 20 μm.

11. The method for manufacturing the silicon carbide semiconductor device according to claim 6 , further comprising a step of annealing said silicon carbide substrate and said silicon dioxide layer after the step of forming said silicon dioxide layer.

12. A silicon carbide substrate comprising:

a silicon carbide single crystal substrate having a first main surface, a second main surface, and a first side end portion, said second main surface being opposite to said first main surface, said first side end portion connecting said first main surface and said second main surface to each other, said first main surface having a width with a maximum value of more than 100 mm; and

a silicon carbide epitaxial layer in contact with a center of said first main surface,

said silicon carbide epitaxial layer including a third main surface and a fourth main surface, said third main surface being in contact with said center of said first main surface, said fourth main surface being opposite to said third main surface,

said fourth main surface having an outer circumferential end portion located closer to said center relative to a boundary between said first main surface and said first side end portion in a direction parallel to said first main surface, and

said first side end portion has a curvature to project in an outer circumferential direction when viewed in a cross section, wherein

said silicon carbide epitaxial layer includes a second side end portion connecting said third main surface and said fourth main surface to each other,

when viewed in a cross section, said second side end portion is formed to have a curvature in conformity with said first side end portion, and

said second side end portion has a radius of curvature substantially the same as a radius of curvature of said first side end portion when viewed in a cross-section.

13. The silicon carbide substrate according to claim 12 , wherein said silicon carbide epitaxial layer has a thickness of not less than 5 μm on said center of said first main surface.

14. A silicon carbide semiconductor device comprising:

the silicon carbide substrate recited in claim 12 ; and

a silicon dioxide layer disposed to face said silicon carbide epitaxial layer.

15. The silicon carbide semiconductor device according to claim 14 , wherein said silicon dioxide layer is an interlayer insulating film.

16. The silicon carbide semiconductor device according to claim 14 , wherein said silicon dioxide layer has a thickness of not less than 0.8 μm and not more than 20 μm.