Patent ID: 7737002

Claim:
A method of dividing a wafer along a plurality of streets by moving the wafer at a predetermined rate while a laser beam whose focal spot is elliptic is applied along the streets formed on the wafer, the wafer having a plurality of areas defined by the plurality of streets formed in a lattice on a front surface, devices formed in the defined areas and an adhesive film for die bonding on a rear surface of the wafer and put on a dicing tape affixed to an annular frame, the method comprising: forming grooves reaching the rear surface of the wafer, from the front surface of the wafer along the streets in the wafer, by applying a first laser beam whose elliptic focal spot has a ratio of the long axis to the short axis of 15 to 20:1; and dividing the adhesive film along the grooves formed by the first laser beam by applying a second laser beam, whose elliptic focal spot has a ratio of the long axis to the short axis of 60 to 70:1, to the adhesive film through the grooves.