US Patent 7655541 Wafer processing method and laser processing apparatus

In a wafer processing method for penetrating a wafer by use of a laser processing apparatus including a chuck table for holding the wafer, laser beam irradiation means for irradiating the wafer held on the chuck table with a laser beam, and imaging means for imaging the wafer held on the chuck table, the chuck table includes a chuck table main body, a holding member disposed on an upper surface of the chuck table main body and having a holding surface for holding an entire surface of the wafer, the holding member comprising a transparent or translucent member, and a light emitting body disposed laterally of a side of the holding member opposite to the holding surface. The wafer processing method comprises irradiating a predetermined processing region of the wafer held on the chuck table with the laser beam to perform the penetration in a predetermined manner, then lighting the light emitting body, with the wafer being held on the chuck table, imaging the processing region by the imaging means, and determining acceptance or rejection of the penetration based on whether or not light has passed through the processing region.