Processing method of wafer

A processing method of a wafer having an effective area formed on a front surface thereof and a chamfered portion formed at an outer periphery thereof and surrounding the effective area, the processing method comprising:

• a modified layer forming step of irradiating the wafer, from a back surface thereof, with a laser beam of a wavelength having transmissivity for the wafer with a focal point of the laser beam positioned inside a boundary portion between the effective area and the chamfered portion, whereby a modified layer is formed along the chamfered portion;
• a chamfered portion removing step of, after performing the modified layer forming step, applying an external force to the outer periphery of the wafer to remove the chamfered portion;
• and
• a processing step of grinding the back surface of the wafer to process the wafer to a desired thickness,
• wherein the modified layer forming step includes
• a first step of irradiating the wafer with the laser beam with the focal point of the laser beam positioned inside the boundary portion between the effective area and the chamfered portion such that a first modified layer is formed relatively deep, with cracks formed extending to the front surface of the wafer, and
• a second step of irradiating the wafer with the laser beam with the focal point of the laser beam positioned inside the boundary portion between the effective area and the chamfered portion such that a second modified layer is formed relatively shallow, adjacent and on an outer or inner side of the first modified layer, with cracks formed not extending to the front surface of the wafer, and
• the chamfered portion is bent, from a side of the front surface toward a side of the back surface, with the first modified layer as a start point.