Abstract: A processing method for a wafer having a plurality of streets inclined at 45° relative to a cleavage direction including a laser processing step of positioning a focusing point of a laser beam with a wavelength as to be transmitted through the wafer in the inside of the wafer, and applying the laser beam along the streets to form a plurality of modified layers, overlapping with one another in the wafer thickness direction, inside the wafer along each of the streets. In the laser processing step, m modified layers (m is a natural number not less than n·?2) are formed overlapping with one another in the wafer thickness direction, where n (n is a natural number) is the number of modified layers needing to be formed overlapping with one another in a wafer thickness direction when dividing a wafer having a plurality of streets parallel to a cleavage direction.

Abstract: A processing method for a wafer having a plurality of streets inclined at 45° relative to a cleavage direction including a laser processing step of positioning a focusing point of a laser beam with a wavelength as to be transmitted through the wafer in the inside of the wafer, and applying the laser beam along the streets to form a plurality of modified layers, overlapping with one another in the wafer thickness direction, inside the wafer along each of the streets. In the laser processing step, m modified layers (m is a natural number not less than n·?2) are formed overlapping with one another in the wafer thickness direction, where n (n is a natural number) is the number of modified layers needing to be formed overlapping with one another in a wafer thickness direction when dividing a wafer having a plurality of streets parallel to a cleavage direction.

Abstract: A wafer processing method is provided. The wafer processing method includes a first laser processing step of forming a first modified layer inside the wafer by applying a laser beam at a wavelength which transmits the wafer along first projected division lines, a second laser processing step of forming a second modified layer inside the wafer excluding non-processed regions in intersecting regions where the first and second projected division lines intersect each other by applying a laser beam at a wavelength which transmits the wafer along the second projected division lines, and a grinding step of grinding a reverse side of the wafer to thin the wafer to a predetermined thickness and at the same time dividing the wafer into a plurality of chips starting from the first and second modified layers. In the second laser processing step, no second modified layers are formed in the non-processed regions.