Formation of surface microcrack for separation of nonmetallic wafers into chips

In recent years a technology for a high quality separation of nonmetallic m aterials into chips using a surface ("blind") microcrack attracted consider able attention in the electronic industry. In this method a wafer is positi oned on the translated X-Y table and is heated by a laser beam up to a temp erature of the order of 300-400 degreesC. The wafer is then cooled by an ai r-water spray, and a surface microcrack is formed due to relaxation of the thermal stresses. The initial microcrack with a depth of the order of sever al hundred microns then propagates in a subsurface region of a wafer and fo llows the path of the laser beam. Theoretical modeling based on the solutio n of the equations of thermal elasticity was performed to determine the dis tributions of temperature and thermal stresses that cause formation of an " edge" microcrack (at the edge of wafer) followed by its transformation into a surface microcrack. The results of thermal stresses analysis are in an a greement with experimental observations.