US Patent 8685838 Laser beam machining method

A laser processing method which can accurately cut an object to be processed along a line to cut is provided. A modified region 7 formed by multiphoton absorption forms a cutting start region 8 within an object to be processed 1 along a line to cut 5. Thereafter, the object 1 is irradiated with laser light L2 absorbable by the object 1 along the line to cut 5, so as to generate fractures 24 from the cutting start region 8 acting as a start point, whereby the object 1 can accurately be cut along the line to cut 5. Expanding an expandable film 19 having the object 1 secured thereto separates individual chips 25 from each other, which can further improve the reliability in cutting the object 1 along the line to cut 5.