US Patent 7364986 Laser beam processing method and laser beam machine

A laser beam processing method comprising the step of processing-feeding a wafer having devices which are formed in a large number of areas sectioned by streets arranged in a lattice pattern on the front surface while a laser beam capable of passing through the wafer is applied to the wafer to form deteriorated layers along the streets in the inside of the wafer, wherein the laser beam is applied at a predetermined angle toward a direction intersecting at right angles to the processing-feed direction relative to a direction perpendicular to the laser beam applied surface of the wafer.