Breaking of silicon wafer by irradiation of YAG laser

Cutting of brittle materials such as silicon wafer is usually made with a diamond scriber or a diamond thin blade wheel. It is said that the mechanical cutting of silicon wafer using the blade leads to lower cutting quality. A non-contacting cutting method using a CO2 laser is recently being studied enthusiastically. Precision breaking of silicon wafer, however, has not been made. Breaking of silicon wafer with a YAG laser was studied at room temperature under water cooling of lapping surface. It was found from the experiments that the breaking of silicon wafer occurred through two stages of crack initiation and propagation. Meandering of the main crack is accompanied with some branching cracks which deteriorate the breaking quality of silicon wafer. Breaking mode is dependent strongly upon laser power, table feed rate and cooling condition.