Development of a high-frequency pulse laser irradiation system for repairing silicon wafers damaged by abrasive machining processes

A four-axis numerically controlled precision stage equipped with a high-frequency nanosecond pulsed Nd:YAG laser system was developed for processing grinding-damaged silicon wafers. The resulting specimens were characterised using a white-light interferometer, a micro-Raman spectroscope and a transmission electron microscope. The results indicate that around the laser beam centre where the laser energy density is sufficiently high, the grinding-induced amorphous silicon was completely transformed into the single-crystal structure. The optimum conditions for one-and two-dimensional overlapping irradiation were experimentally obtained for processing large-diameter silicon wafers. It was found that the energy density level required for completely removing the dislocations is higher than that for recrystallising the amorphous silicon. After laser irradiation, the surface unevenness has been remarkably smoothed.