Protective film and back grinding method for semiconductor wafer

A back grinding method for a semiconductor wafer, the method comprising:

• a sticking step of sticking a protective film to a surface of a semiconductor wafer on which a circuit is formed;
• a sucking step of sucking the semiconductor wafer to the fixture via the protective film, with the protective film interposed between the semiconductor wafer and the fixture sucking the semiconductor wafer;
• and
• a grinding step of grinding a back surface of the semiconductor wafer in a state where the semiconductor wafer is sucked to the fixture via the protective film,
• wherein the protective film includes a pressure-sensitive adhesive layer, a base material layer, and an auxiliary layer,
• the pressure-sensitive adhesive layer is a layer to be stuck to the semiconductor wafer,
• the auxiliary layer is a layer to be contact to the fixture, and
• the semiconductor wafer has a level difference on an outer peripheral edge of the surface on which the circuit is formed.