Patent 7763526 was granted and assigned to Denso on July, 2010 by the United States Patent and Trademark Office.
A laser beam is applied to an interior of a wafer through a top surface to form modified areas in a plurality of layers of modified area groups. Intervals of the modified areas in one of the layers of modified area groups differ from intervals of the modified areas in another one of the layers of the modified area groups, which is closer to the top surface of the wafer in comparison to the one of the layers of the modified area groups.