Slip damage of silicon wafers subjected to continuous infrared laser irradiation

Abstract

Laser irradiation can cause damage to solids, such as slipping, cracking, melting, and ablation. Silicon crystals are brittle, so slipping is a serious problem because it can easily result in fracture. This study investigates the amount of continuous near-infrared (NIR) laser irradiance that induces slip damage in a single-crystal silicon wafer. For this purpose we developed a simulation model based on heat transfer and thermo-elastic analyses. To verify the simulation model, silicon wafer specimens were irradiated by a fiber laser beam (of wavelength 1065 nm), and the surface morphology after laser beam irradiation was inspected using optical microscopy (OM). The irradiation time was fixed at 10 s, and nine different irradiances from 180 W/cm2 to 380 W/cm2 were tested in steps of 25 W/cm2. No slip surface was found after exposure to the irradiances up to 230 W/cm2, but straight slips in the <110> direction appeared at the irradiances of 255 W/cm2 and above. These experimental findings agreed well with the simulation.