Patent ID: 7538048

Claim:
A laser beam processing method of forming deteriorated regions in a wafer along a dividing line, comprising the steps of: holding a wafer on a chuck; producing a pulse laser beam capable of passing through the wafer; transmitting the pulse laser beam to a path distribution means; dividing the pulse laser beam by the path distribution means into a first pulse laser beam and a second pulse laser beam; distributing the first pulse laser beam to a first path and the second pulse laser beam to a second path by the path distribution means; applying the first pulse laser beam and the second pulse laser beam to the wafer in such a manner that a focusing point of the first pulse laser beam and a focusing point of the second laser beam are moved along the dividing line to form deteriorated regions in the wafer along the dividing line and in such a manner that the first pulse laser beam and the second pulse laser beam are applied to the wafer alternately with a time lag therebetween; and displacing the focusing point of one of the first pulse laser beam and the second pulse laser beam so that the focusing points of the first and second pulse laser beams are displaced from each other in the wafer, in the direction of thickness of the wafer.