K. Moriya et al., DETECTION AND IDENTIFICATION OF NEAR-SURFACE MICROPRECIPITATES IN SILICON-WAFERS BY LASER SCATTERING TOMOGRAPHY, JPN J A P 1, 34(10), 1995, pp. 5721-5728
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).