Laser recovery of grinding-induced subsurface damage in the edge and notch of a single-crystal silicon wafer

Abstract

The edges and notches of silicon wafers are usually machined by diamond grinding, and the grindinginduced subsurface damage causes wafer breakage and particle contamination problems. However, the edge and notch surfaces have large curvature and sharp corners, thus it is difficult to be finished by chemo-mechanical polishing. In this study, a nanosecond pulsed Nd:YAG laser was used to irradiate the edge and notch of a boron-doped single-crystal silicon wafer to recover the grinding-induced subsurface damage. The reflection loss and the change of laser fluence when irradiating a curved surface were considered, and the damage recovery behavior was investigated. The surface roughness, crystallinity, and hardness of the laser recovered region were measured by using white light interferometry, laser micro-Raman spectroscopy, and nanoindentation, respectively. The results showed that after laser irradiation the damaged region was recovered to a single-crystal structure with nanometric surface roughness, and the surface hardness was also improved. This study demonstrates that laser recovery is a promising postgrinding process for improving the surface integrity of the edge and notch of silicon wafers.

Research on laser repair technology for surface defects of flywheel disc steel plate

“…Bhaduri et al [9] studied the effects of laser energy density and pulse overlap parameters on the surface roughness of the workpiece obtained after laser polishing of flat 3D printed stainless steel samples, and under optimized settings, the maximum reduction in roughness exceeds 94%. Niitsu et al [10] used nanosecond pulse laser to irradiate the edges and notches of boron doped monocrystalline silicon wafers after diamond grinding. Through laser irradiation with a certain laser energy density, microcracks in the chip notches were eliminated.…”