Recovery of microstructure and surface topography of grinding-damaged silicon wafers by nanosecond-pulsed laser irradiation

Abstract

Single crystalline silicon wafers whose surfaces were machined by diamond grinding were irradiated by a nanosecond-pulsed Nd:YAG laser. Changes in the subsurface crystallinity and surface topography were investigated by transmission electron microscopy and atomic force microscopy. It was found that the grinding process gave rise to amorphous layers, dislocations and micro cracks. However, all of this damage could be eliminated by a single laser pulse of suitable energy density, which also led to a remarkable amount of smoothing of the wafer surface. When excessively high energy densities were used, tiny particles were found to form on the wafer surface. It is speculated that these particles are produced by the recondensation of silicon boiled away from the wafer surface during the laser pulse. The temperature rise during laser irradiation was estimated using a simplified model. The results obtained in this study suggest that nanosecond-pulsed laser irradiation may be an effective approach for processing grinding-damaged silicon wafers.