Patent ID: 8722516

Claim:
A laser processing method for cutting a wafer including a single-crystal sapphire substrate having a C-plane as a principal surface along first and second lines to cut the wafer, the method comprising: a first step of irradiating the single-crystal sapphire substrate with a pulsed laser light while locating a converging point within the substrate, and relatively moving the converging point of the pulsed laser light along the first line arranged along an M-plane of the single-crystal sapphire substrate, so as to form a first modified region within the single-crystal sapphire substrate along the first line; and a second step of irradiating the single-crystal sapphire substrate with the pulsed laser light while locating the converging point within the substrate, and relatively moving the converging point of the pulsed laser light along the second line arranged along an A-plane of the single-crystal sapphire substrate, so as to form a second modified region within the single-crystal sapphire substrate along the second line; wherein, in the first step, a modified part is formed by irradiation with one pulse of the pulsed laser light, and a plurality of the modified parts are arranged at a first formation pitch along the first line, so as to form the first modified region; wherein, in the second step, a plurality of the modified parts are arranged with a second formation pitch narrower than the first formation pitch along the second line, so as to form the second modified region, wherein the first formation pitch is a value obtained by dividing a first relative speed of the pulsed laser light by a repetition frequency of the pulsed laser light in the first step, and the second formation pitch is a value obtained by dividing a second relative speed of the pulsed laser light by a repetition frequency of the pulsed laser light in the second step.