Formation of surface microcrack for separation of nonmetallicwafers into chips

In recent years a technology for a high quality separation qf nonmetallic materials intochips using a surface (“blind”) microcrack attracted considerable attention in the elec-tronic industry. In this method a wafer is positioned on the translated X-Y table and isheated by a laser beam up to a temperature of the order of 300-400°C. The wafer is thencooled by an air-water spray, and a surface microcrack is formed due to relaxation of thethermal stresses. Tne initial microcrack with a depth of the order of sev eral hundred microns then propagates in a subsurface region of a wafer and follows the path of thelaser beam. Theoretical modeling based on the solution of the equations of thermalelasticity was performed to determine the distributions of temperature and thermal stresses that cause formation of an “edge” microcrack (at the edge of a wafer) followedby its transformation into a surface microcrack. The results of thermal stresses analysisare in an agreement with experimental observations.