Patent ID: 7763526

Claim:
A wafer cutting and dividing method comprising: focusing a pulsed laser beam to a corresponding focal point at a corresponding depth in an interior of a wafer through a first surface of the wafer; relatively moving the focal point of the laser beam relative to the wafer along a predetermined cutting line of the wafer to form a plurality of modified areas by multiphoton absorption from the laser beam in such a manner that the modified areas are arranged at corresponding constant intervals in a direction parallel to the first surface and a second opposite surface of the wafer; sequentially changing the depth of the focal point of the laser beam and repeating the relatively moving of the focal point of the laser beam every time the depth of the focal point of the laser beam is changed, so that there is formed a plurality of layers of modified area groups, which are arranged one after another in a depth direction between the first surface and a second surface of the wafer, and the intervals of the modified areas in one of the plurality of layers of the modified area groups differ from the intervals of the modified areas in another one of the plurality of layers of the modified area groups, which is closer to the first surface of the wafer in comparison to the one of the plurality of layers of the modified area groups; and cutting and dividing the wafer along the predetermined cutting line through cracking of the wafer, which is started at the plurality of layers of the modified area groups formed along the predetermined cutting line.