Silicon carbide epitaxial substrate and method of manufacturing the same

A silicon carbide epitaxial substrate comprising:

• a silicon carbide substrate;
• and
• an epitaxial layer formed on an upper surface of the silicon carbide substrate,
• wherein a plurality of surface defects and a plurality of threading screw dislocations are provided on an upper surface of the epitaxial layer,
• wherein the plurality of surface defects includes minute surface defects that are defects satisfying L<d/tan θ where a length of the surface defect in plan view is denoted as L, a thickness of the epitaxial layer is denoted as d, and an off-angle of the silicon carbide substrate is denoted as θ,
• wherein, in a graph created using a plurality of pieces of data with a horizontal axis representing a density of the threading screw dislocations and a vertical axis representing a density of the minute surface defects,
• a slope of an approximate curve when linear fitting is performed by the least squares method with an intercept of the vertical axis fixed at 0 is smaller than 0.05, and
• wherein the plurality of pieces of data is obtained by plotting, on the graph, measurement results of the density of the threading screw dislocations and the density of the minute surface defects in each of a plurality of regions when the upper surface of the epitaxial layer is divided into the plurality of regions.

A method of manufacturing a silicon carbide epitaxial substrate, comprising the steps of:

• (a) preparing a silicon carbide substrate;
• and
• (b) forming an epitaxial layer on an upper surface of the silicon carbide substrate in a growth chamber of a deposition apparatus,
• wherein, in the step (b), a silicon-based gas and a carrier gas are supplied into the growth chamber through a first pipe, and a carbon-based gas and a carrier gas are supplied into the growth chamber through a second pipe,
• wherein, in the step (b), the epitaxial layer is continuously formed on the upper surfaces of 25 or more silicon carbide substrates at a deposition speed faster than 40 μm/h,
• wherein a plurality of surface defects and a plurality of threading screw dislocations are provided on an upper surface of the epitaxial layer,
• wherein the plurality of surface defects includes minute surface defects that are defects satisfying L<d/tan θ where a length of the surface defect in plan view is denoted as L, a thickness of the epitaxial layer is denoted as d, and an off-angle of the silicon carbide substrate is denoted as θ, and
• wherein, in the step (b), a flow rate of the carrier gas in the first pipe and a flow rate of the carrier gas in the second pipe are adjusted so that a density of the minute surface defects becomes 100 counts/cm2 or less.