Supporting substrate, bonded substrate, method for manufacturing supporting substrate, and method for manufacturing bonded substrate

A bonded substrate comprising:

• a single crystalline wafer made of a single crystalline body;
• and
• a supporting substrate to be bonded on the single crystalline wafer,
• wherein the supporting substrate has:
• a silicon carbide polycrystalline substrate made of a silicon carbide polycrystalline body;
• and a coating layer to be evaporated on the silicon carbide polycrystalline substrate,
• the coating layer is made of silicon carbide or silicon, and comes into contact with the single crystalline wafer, and
• an arithmetic average roughness of a surface of the coating layer that comes into contact with the single crystalline wafer is 1 nanometer or less.

A method for manufacturing a bonded substrate which has a single crystalline wafer made of a single crystalline body and a supporting substrate to be bonded on the single crystalline wafer, the method comprising the steps of:

• evaporating silicon carbide or silicon on a silicon carbide polycrystalline substrate made of a silicon carbide polycrystalline body;
• applying grinding onto a face onto which the evaporation is made, in the silicon carbide polycrystalline substrate, so as to allow an arithmetic average roughness of the evaporated face to be 1 nanometer or less;
• and
• bonding a face to which the grinding is applied and the single crystalline wafer with each other.