SILICON CARBIDE EPITAXIAL SUBSTRATE, METHOD OF MANUFACTURING EPITAXIAL SUBSTRATE, AND METHOD OF MANUFACTURING SILICON CARBIDE SEMICONDUCTOR DEVICE
A silicon carbide epitaxial substrate includes a silicon carbide substrate and a silicon carbide epitaxial layer. The silicon carbide epitaxial layer is provided on the silicon carbide substrate. The silicon carbide epitaxial layer has a boundary layer, a buffer layer, and a drift layer. The boundary layer is provided on the silicon carbide substrate. The buffer layer is provided on the boundary layer. The drift layer is provided on the buffer layer. A concentration of an n type impurity in the buffer layer is 3×10 18 /cm 3 or more. A concentration of an n type impurity in the boundary layer is higher than the concentration of the n type impurity in the buffer layer.
1 . A silicon carbide epitaxial substrate comprising:
a silicon carbide substrate; and
a silicon carbide epitaxial layer provided on the silicon carbide substrate, wherein
the silicon carbide epitaxial layer includes
a boundary layer provided on the silicon carbide substrate,
a buffer layer provided on the boundary layer, and
a drift layer provided on the buffer layer,
a concentration of an n type impurity in the buffer layer is 3×10 18 /cm 3 or more, and
a concentration of an n type impurity in the boundary layer is higher than the concentration of the n type impurity in the buffer layer.
2 . The silicon carbide epitaxial substrate according to claim 1 , wherein the concentration of the n type impurity in the boundary layer is higher than a concentration of an n type impurity in the silicon carbide substrate.
3 . The silicon carbide epitaxial substrate according to claim 1 , wherein a value obtained by subtracting the concentration of the n type impurity in the buffer layer from the concentration of the n type impurity in the boundary layer is 1×10 18 /cm 3 or more.
4 . The silicon carbide epitaxial substrate according to claim 1 , wherein a thickness of the boundary layer is 0.1 μm or more and 5 μm or less.
5 . The silicon carbide epitaxial substrate according to claim 1 , wherein the concentration of the n type impurity in the buffer layer is higher than a concentration of an n type impurity in the drift layer.
6 . The silicon carbide epitaxial substrate according to claim 1 , wherein the concentration of the n type impurity in the boundary layer is 5×10 18 /cm 3 or more and 1×10 20 /cm 3 or less.
7 . The silicon carbide epitaxial substrate according to claim 1 , wherein the concentration of the n type impurity in the buffer layer is 1×10 19 /cm 3 or less.
8 . The silicon carbide epitaxial substrate according to claim 1 , wherein a concentration of an n type impurity in the drift layer is 1×10 15 /cm 3 or more and 5×10 16 /cm 3 or less.
9 . A method of manufacturing an epitaxial substrate, the method comprising:
preparing the silicon carbide epitaxial substrate according to claim 1 ;
measuring a distance from an interface between the boundary layer and the buffer layer to a surface of the silicon carbide epitaxial layer using the silicon carbide epitaxial substrate;
determining a growth condition based on the distance measured; and
performing epitaxial growth using the growth condition determined.
10 . A method of manufacturing a silicon carbide semiconductor device, the method comprising:
manufacturing an epitaxial substrate using the method of manufacturing an epitaxial substrate according to claim 9 ; and
processing the epitaxial substrate.