Patent ID: 8617964
Filing Date: 2013-12-31
Classification: B23K,B28D,H01L

Abstract:
1. A laser processing method of converging laser light within a silicon wafer having a thickness t (500 μm <t) with a condenser lens so as to form a plurality of rows of modified regions to become a cutting start point within the silicon wafer along a cutting line for cutting the silicon wafer, the method comprising the steps of: forming a first modified region along the cutting line in a first area having a depth of 350 μm to 500 μm from a laser light entrance surface of the silicon wafer by locating a converging point of the laser light in the first area; and forming a second modified region along the cutting line in a second area having a depth of 0 μm to 250 μm from the laser light entrance surface by locating the converging point in the second area; wherein, when forming the first modified region, the laser light is converged within the silicon wafer so as to cancel a spherical aberration to occur in response to a depth from the laser light entrance surface, and in the laser light emitted from the condenser lens, the converging position of center rays and converging position of marginal rays are restrained from deviating from each other in the thickness direction of the silicon wafer, and thereby an the influence of the spherical aberration is reduced.