It was recalled that defects which were just below the mirror surface of a Si wafer, grown by using the Czochralski method, were critically important for epitaxial growth at the surface. The use of internal total reflection of an infra-red laser beam permitted only the light which was scattered by defects and tiny inclusions in the denuded zone of the wafer to be observed through the surface. This was because some of the scattered light had an incident angle that was smaller than the critical value, while the unscattered part of the beam was totally reflected and therefore did not emerge from the wafer. A background brightness was caused by light scattering from tiny inclusions such as interstitial O atoms in the zone. Inhomogeneity of this background indicated fluctuations in the distribution of the defects.

N.Nango, H.Furuya, J.Furukawa, T.Ogawa: Journal of Applied Physics, 1995, 78[4], 2892-3