US Patent 9076855 Laser machining method

An object to be processed 1 is irradiated with laser light L along a line to cut 5a while locating a converging point within the object 1, so as to form a modified region 7a. Thereafter, the irradiation with the laser light L is performed again along the line 5a, so as to form a modified region 7b between a front face 3 and the first modified region 7a in the object 1 and generate a fracture Cb extending from the modified region 7b to the front face 3. Therefore, a deflecting force F1 occurring when forming the modified region 7a in the object 1 can be released and canceled out by the fracture Cb. As a result, the object 1 can be inhibited from deflecting.