DETECTION AND IDENTIFICATION OF NEAR-SURFACE MICROPRECIPITATES IN SILICON-WAFERS BY LASER SCATTERING TOMOGRAPHY

A nondestructive measurement system for characterizing near-surface (0 to 100 mu m) microprecipitates in silicon wafers using laser scatteri ng tomography has been developed. A near-infrared laser beam (lambda=1 mu m) is focused to about 4 mu m in diameter and introduced into the wafer from an inclined direction through the polished surface. The sca ttered light is also observed from the polished side. The scattered li ght has a complicated signal, because the scattered light from the nea r-surface microdefects, that from the haze related to the surface micr oroughness, and that from the dust on the surface are mixed. By using a polarization analysis method, the scatterings from the haze, dust an d microdefects are clearly distinguished. The scattering from the subs urface (0 to 5 mu m) region is also identified as that due to dust and microprecipitates by using a short-wavelength laser (lambda=680 nm).