US Patent 7141443 Semiconductor wafer dividing method utilizing laser beam

A method which can divide a semiconductor wafer sufficiently precisely along a street by use of a laser beam, while fully avoiding or suppressing contamination of circuits formed in rectangular regions on the face of the semiconductor water, and without causing chipping to the rectangular regions on the face. A laser beam is applied from beside one of the back and the face of a semiconductor substrate and focused onto the other of the back and the face of the semiconductor substrate, or the vicinity thereof, to partially deteriorate at least a zone ranging from the other of the back and the face of the semiconductor substrate to a predetermined depth.