Epitaxial silicon carbide single crystal wafer and process for producing the same
An epitaxial silicon carbide single crystal wafer having a small depth of shallow pits and having a high quality silicon carbide single crystal thin film and a method for producing the same are provided. The epitaxial silicon carbide single crystal wafer according to the present invention is produced by forming a buffer layer made of a silicon carbide epitaxial film having a thickness of 1 μm or more and 10 μm or less by adjusting the ratio of the number of carbon to that of silicon (C/Si ratio) contained in a silicon-based and carbon-based material gas to 0.5 or more and 1.0 or less, and then by forming a drift layer made of a silicon carbide epitaxial film at a growth rate of 15 μm or more and 100 μm or less per hour. According to the present invention, the depth of the shallow pits observed on the surface of the drift layer can be set at 30 nm or less.
1. An epitaxial silicon carbide single crystal wafer comprising:
a silicon carbide single crystal substrate having an off angle of 4° or less, which is an angle tilted in the <11-20> direction with respect to a (0001) plane;
a buffer layer, formed on the silicon carbide single crystal substrate, having a doping density of 1×10 18 atms/cm 3 or more and 1×10 19 atms/cm 3 or less and consisting of a silicon carbide epitaxial film having a thickness of 5 μm or more and 10 μm or less; and
a drift layer, formed on the buffer layer, having a doping density of 1×10 15 atms/cm 3 or more and 1×10 17 atms/cm 3 or less and consisting of a silicon carbide epitaxial film having a thickness of 10 μm or more and 30 μm or less,
wherein a depth of shallow pits on the surface of the drift layer is 19 nm or less, and
wherein the shallow pits are formed by a screw dislocation of the silicon carbide single crystal wafer.
2. The epitaxial silicon carbide single crystal wafer according to claim 1 ,
wherein when a Schottky barrier diode is formed by providing a Ni-based ohmic electrode on a side of the silicon carbide single crystal substrate and a Ni-based Schottky electrode on a side of the drift layer, a leakage current at a reverse applied voltage of 400 V becomes 1×10 −11 A/cm 2 or more and 1×10 −8 A/cm 2 or less.