US Patent 7776721 Laser processing method for gallium arsenide wafer

A laser processing method for a gallium arsenide wafer of radiating a laser beam along streets formed in lattice on a surface of a gallium arsenide substrate, and cutting-off the gallium arsenide wafer along the streets includes a wafer supporting step for sticking a rear surface of the gallium arsenide substrate on a protective member, a debris shielding coating step for coating the surface of the gallium arsenide substrate with a debris shielding film, a laser-processed trench forming step for radiating a laser beam along the streets from the debris shielding film side to the gallium arsenide substrate, thereby forming laser-processed trenches each not reaching the rear surface, and a cutting-off step for radiating the laser beam along the laser-processed trenches to the gallium arsenide substrate, thereby forming cutting-off trenches each reaching the rear surface.