Non-destructive diagnostic techniques for oxygen precipitates in Czochralski silicon

Abstract

This work investigates the determination of oxygen precipitate density in silicon using non-destructive methods, based essentially on electrical and optical techniques. Regarding electrical techniques, minority carrier diffusion length measurements by means of surface photo voltage or electrolytical metal tracer methods to determine the density of oxygen precipitates in p-type silicon wafers is evaluated, taking advantage of the activity of oxygen precipitates as recombination centres for minority carriers. Regarding optical techniques, the scanning infra-red microscope is considered, which can detect oxygen precipitates in silicon exploiting their effectiveness as light scattering centres. These techniques are compared with the traditional etching technique, considering samples in a wide range of precipitate density (5×106–1011cm−3) and submitted to a wide variety of thermal treatments. Correlations are discussed with the support of transmission electron microscopy, X-ray diffraction and infrared spectroscopy observations, which provide complementary information on size, morphology and matrix stress of the oxygen precipitates.