Method for manufacturing silicon carbide semiconductor device, method for manufacturing semiconductor base, silicon carbide semiconductor device, and device for manufacturing silicon carbide semiconductor device

A method for manufacturing a semiconductor base comprising:

• a step for thinning a silicon carbide wafer by reducing a thickness of the silicon carbide wafer from a back surface side thereof;
• a step for providing a metal layer on the back surface of the thinned silicon carbide wafer;
• and
• a step for irradiating the metal layer with laser light, while applying an external force such that the silicon carbide wafer and the metal layer are planarized, to form the carbide layer obtained by a reaction with carbon in the silicon carbide wafer, on a back surface side of the metal layer,
• wherein the carbide layer includes a high-density portion having high carbide density and a low-density portion having low carbide density, and
• wherein the high-density portion is provided along two different directions which are in-plane directions of the carbide layer.

A silicon carbide semiconductor device comprising:

• a silicon carbide wafer,
• a front-surface electrode provided on a front surface side of the silicon carbide wafer,
• a carbide layer provided on aback surface of the silicon carbide wafer which has been thinned, and
• a back-surface electrode provided on a back surface side of the carbide layer
• wherein the carbide layer includes a high-density portion having high carbide density and a low-density portion having low carbide density, and
• wherein the high-density portion is provided along two different directions which are in-plane directions of the carbide layer.