EFFECT OF OXYGEN CONCENTRATION ON DIFFUSION LENGTH IN CZOCHRALSKI ANDMAGNETIC CZOCHRALSKI SILICON

This paper reports some new results on the influence of oxygen aggrega tion phenomena in the 450-850 degrees C range on the diffusion length of minorities in both Czochralski (Cz) and magnetic Czochralski silico n. The features of the oxygen aggregation phenomena were studied by in frared spectroscopy at 20 K and the effect of these processes an the d iffusion length was monitored by surface photovoltage measurements at 300 K. The results show that in Cz silicon the formation of thermal do nors at 450 degrees C is not associated with a detectable increase of the recombination activity, but that thermal donors are the precursors of other oxygen species, which grow during any further heat treatment . It was shown, moreover, that selfinterstitials injected from a surfa ce oxide inhibit the oxygen segregation, in good agreement with predic tions in the literature concerning the 'volume exigency' of oxygen seg regation processes. Masked evidence of the influence of the cooling ra te on the diffusion length was observed at 850 degrees C, where the li fetime of heat treated Cz silicon was shown to be longer for a slow co oling process.