Influence of rapid thermal annealing and internal gettering on Czochralski-grown silicon .1. Oxygen precipitation

The effect of rapid thermal annealing at 1200 degrees C as a pretreatment on the precipitation of oxygen during a three-step internal gettering process is studied thanks to infrared analyses. The influence of both the duration and the ambient of this pretreatment is considered. We define a limit duration of the rapid thermal annealing from which the further precipitation is greatly enhanced through a precipitation path leading to the formation of quasispherical precipitates different from the platelets. It is also shown that hydrogen introduced during the rapid thermal anneal delays the oxygen precipitation during the internal gettering process. Finally, considering the inefficiency of the internal gettering of chromium after a rapid thermal annealing at 1200 degrees C under argon/hydrogen, a new interpretation is proposed: a rapid thermal annealing would produce a modification in the oxygen precipitation path, leading to the formation of precipitates which would not be suitable for an efficient gettering effect. (C) 1996 American Institute of Physics.