Patent ID: 7566635

Claim:
A substrate dividing method comprising the steps of: irradiating a substrate with laser light while positioning a light-converging point within the substrate, so as to form a modified region within the substrate, and causing the modified region to form a starting point region for cutting along a line along which the substrate should be cut, in the substrate inside by a predetermined distance from a laser light incident face of the substrate; placing a protective film over a front face of the substrate after the step of forming the starting point region for cutting; grinding a rear face of the substrate after the step of placing the protective film such that the substrate attains a predetermined thickness, so as to divide the substrate into a plurality of chips along the line along which the substrate should be cut; attaching an expansion film to rear faces of the chips after the step of dividing the substrate into the chips; and expanding the expansion film after the step of attaching the expansion film, so as to separate the chips from each other.