Laser cutting of silicon wafer by pulsed Nd:YAG source

Nowadays, silicon wafer is employed as substrate material for the fabrication of micro-electro and micromechanical components. Since silicon is a nominally brittle material, cutting of complex shapes remains a critical topic to study. Laser cutting represents a promising alternative. It does not involve any mechanical cutting force and tool wear. Moreover, thanks to the small spot diameter, laser cutting allows to realize very small and complex shapes too. However, during laser cutting, different kinds of defects can be generated depending on the beam-material interaction phenomena (ablation, melting and brittle cracking). The aim of this work is to investigate the influence of the process parameters on the kerf geometry and defects in cutting operation of a 0.75 mm thick silicon wafer using a pulsed Nd:YAG, working in the regime of short pulses. Cutting tests were carried out varying mean power, pulse duration, pulse energy and cutting speed. Experimental results showed that a pulsed Nd:YAG laser, with a nominal power of 150W, can be successfully used to cut 0.75 mm silicon wafer plates obtaining a kerf of about 200 μm at a maximum cutting speed of 15 mm/s (0.9 m/min). However, an accurate selection of the process parameters is necessary in order to obtain a regular kerf geometry and to avoid defects formation.