US Patent 7919395 Method for separating wafer using two laser beams

A wafer separating method including a laminated member removing step for partially removing a laminated member of a wafer along streets by applying a laser beam to the wafer along the streets, and a cutting step for cutting a substrate of the wafer along the streets after the laminated member removing step. The laminated member removing step includes a first laser processing step for applying a first laser beam along two parallel lines spaced apart from each other in each street, the first laser beam being capable of passing through the laminated member and having an absorption wavelength to the substrate, thereby heating the substrate to generate two cracks in the laminated member by thermal shock so that the two cracks extend along the two parallel lines in each street; and a second laser processing step for applying a second laser beam to a region between the two cracks in the laminated member, the second laser beam having an energy density higher than that of the first laser beam, thereby removing the region between the two cracks in the laminated member to expose the substrate along each street.