SILICON CARBIDE EPITAXIAL SUBSTRATE, METHOD OF MANUFACTURING SILICON CARBIDE EPITAXIAL SUBSTRATE, AND METHOD OF MANUFACTURING SILICON CARBIDE SEMICONDUCTOR DEVICE
A silicon carbide epitaxial substrate includes a silicon carbide substrate, a silicon carbide epitaxial layer, and a bump. The silicon carbide epitaxial layer is located on the silicon carbide substrate. The bump is formed on the silicon carbide epitaxial layer. The silicon carbide epitaxial layer includes a main surface located opposite to a boundary surface between the silicon carbide substrate and the silicon carbide epitaxial layer, and a drift layer that constitutes the main surface. An area density of the bump is 1.0/cm 2 or less on the main surface. A height of the bump is 50 nm or more. A diameter of the bump is 5 μm or more and 30 μm or less. A polytype of silicon carbide of the bump is the same as a polytype of silicon carbide of the silicon carbide epitaxial layer.
1 . A silicon carbide epitaxial substrate comprising:
a silicon carbide substrate;
a silicon carbide epitaxial layer located on the silicon carbide substrate; and
a bump formed on the silicon carbide epitaxial layer, wherein
the silicon carbide epitaxial layer includes a main surface located opposite to a boundary surface between the silicon carbide substrate and the silicon carbide epitaxial layer, and a drift layer that constitutes the main surface,
an area density of the bump is 1.0/cm 2 or less on the main surface,
a height of the bump is 50 nm or more,
a diameter of the bump is 5 μm or more and 30 μm or less, and
a polytype of silicon carbide of the bump is the same as a polytype of silicon carbide of the silicon carbide epitaxial layer.
2 . The silicon carbide epitaxial substrate according to claim 1 , wherein an in-plane uniformity of a carrier concentration in the drift layer is 15% or less.
3 . The silicon carbide epitaxial substrate according to claim 1 , wherein an in-plane uniformity of a carrier concentration in the drift layer is 7% or less.
4 . The silicon carbide epitaxial substrate according to claim 1 , wherein a diameter of the main surface is 150 mm or more.
5 . The silicon carbide epitaxial substrate according to claim 1 , wherein the area density of the bump is 0.5/cm 2 or less.
6 . The silicon carbide epitaxial substrate according to claim 1 , wherein an in-plane uniformity of a thickness of the drift layer is 5% or less.
7 . The silicon carbide epitaxial substrate according to claim 6 , wherein the in-plane uniformity of the thickness of the drift layer is 3% or less.
8 . A method of manufacturing a silicon carbide semiconductor device, the method comprising:
preparing the silicon carbide epitaxial substrate according to claim 1 ; and
processing the silicon carbide epitaxial substrate.
9 . A method of manufacturing a silicon carbide epitaxial substrate, the method comprising:
forming a silicon carbide epitaxial layer on a silicon carbide substrate under a condition of a first C/Si ratio;
forming a surface-modified layer on the silicon carbide epitaxial layer under a condition of a second C/Si ratio; and
removing the surface-modified layer by hydrogen etching, wherein
the second C/Si ratio is less than the first C/Si ratio, and
the removing the surface-modified layer by the hydrogen etching is performed at a temperature of 1600° C. or more and 1800° C. or less for a time of 1 minute or more and 10 minutes or less.
10 . The method of manufacturing the silicon carbide epitaxial substrate according to claim 9 , wherein
a bump formed on the silicon carbide epitaxial layer is a first bump, and a bump formed on the surface-modified layer is a second bump,
an area density of the first bump before the forming the surface-modified layer on the silicon carbide epitaxial layer is more than 1.0/cm 2 ,
an area density of the second bump is 1.0/cm 2 or less, and
the area density of the first bump after the removing the surface-modified layer by the hydrogen etching is less than the area density of the first bump before the forming the surface-modified layer on the silicon carbide epitaxial layer.
11 . The method of manufacturing the silicon carbide epitaxial substrate according to claim 10 , wherein the area density of the first bump before the forming the surface-modified layer on the silicon carbide epitaxial layer is more than 2/cm 2 .
12 . The method of manufacturing the silicon carbide epitaxial substrate according to claim 9 , wherein a thickness of the surface-modified layer in the forming the surface-modified layer on the silicon carbide epitaxial layer is 0.2 μm or more and 1 μm or less.
13 . The method of manufacturing the silicon carbide epitaxial substrate according to claim 9 , wherein the first C/Si ratio is 1.1 or more and 1.8 or less.
14 . The method of manufacturing the silicon carbide epitaxial substrate according to claim 9 , wherein the second C/Si ratio is 0.85 or more and 0.95 or less.