Influence of rapid thermal annealing and internal gettering on Czochralski-grown silicon .2. Light beam induced current study of recombination centers

Results concerning the generation of recombination centers induced by rapid thermal annealing and by the combination of this heat pulse with an internal gettering process are reported. The influence of both the duration and the ambient of the rapid thermal annealing is studied by measurements of the minority-carrier diffusion length. This work shows that (i) a short heat pulse at high temperature is sufficient to induce a strong degradation of this diffusion length. The activation of the pre-existing impurities and a modification of the intrinsic defect population during the annealing may occur, (ii) the rapid thermal annealing has still an influence on the generation of recombination centers after thermal treatments at high temperature and for long durations. Indeed, this memory effect is observed even after the internal process, as observed in a previous work for the oxygen precipitation. However, we conclude that the recombination centers generated cannot be totally correlated with the oxygen precipitation. Introducing hydrogen during the RTA shows that the nature of defects responsible for the modification of the minority carrier diffusion length and oxygen precipitation must be different. (C) 1996 American Institute of Physics.