US Patent 7713845 Laser processing method for wafer

A laser processing method for a wafer such that a laser beam is applied to a work surface of the wafer along a separation line formed on the work surface to thereby form a laser processed groove along the separation line on the work surface by ablation. The laser processing method includes a protective material coating step for coating the work surface of the wafer with a liquid protective material mainly containing a water-soluble silicone oil and a laser processed groove forming step for applying the laser beam to the work surface coated with the protective material along the separation line in the condition that the protective material has fluidity, thereby forming the laser processed groove along the separation line.