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 pretreatm ent on the precipitation of oxygen during a three-step internal getter ing process is studied thanks to infrared analyses. The influence of b oth the duration and the ambient of this pretreatment is considered. W e define a limit duration of the rapid thermal annealing from which th e further precipitation is greatly enhanced through a precipitation pa th leading to the formation of quasispherical precipitates different f rom the platelets. It is also shown that hydrogen introduced during th e rapid thermal anneal delays the oxygen precipitation during the inte rnal gettering process. Finally, considering the inefficiency of the i nternal gettering of chromium after a rapid thermal annealing at 1200 degrees C under argon/hydrogen, a new interpretation is proposed: a ra pid thermal annealing would produce a modification in the oxygen preci pitation path, leading to the formation of precipitates which would no t be suitable for an efficient gettering effect. (C) 1996 American Ins titute of Physics.