US Patent 7622328 Processing method of wafer

A separation groove having a depth corresponding to a finished thickness of a semiconductor chip is formed in a boundary between a device region and an outer peripheral surplus region of a wafer, a protection tape whose adhesion is deteriorated by irradiation of ultraviolet rays is adhered on a surface, a portion of a back surface corresponding to the device region is ground, a thick reinforcing portion is formed on a portion corresponding to the outer peripheral surplus region. Next, only a portion of the protection tape adhered on the reinforcing portion is irradiated with ultraviolet rays, the reinforcing portion 8 is separated from the protection tape and is separated from the device region. A dicing frame is mounted on the back surface of the wafer having only the device region through a dicing tape, and the wafer is divided into semiconductor chips.