US Patent RE45403 Laser processing method

A modified region 7 to become a starting point region for cutting is formed in a GaAs substrate 12 along a line to cut 5 upon radiation with laser light L which is pulsed laser light. As a consequence, the modified region 7 formed in the GaAs substrate 12 along the line to cut 5 is likely to generate fractures in the thickness direction of an object to be processed 1. Therefore, the modified region 7 having an extremely high function as a starting point region for cutting can be formed in the planar object to be processed 1 comprising the GaAs substrate 12.