On the origin of internal gettering suppression in low carbon CZ silicon by rapid thermal annealing

The influence of classic and rapid thermal annealing pretreatments under nitrogen or hydrogenated ambients on thermal donor formation and on the further oxygen nucleation step were studied. A rapid thermal annealing at 1200 degree C under a nitrogen ambient delayed the formation of thermal donors. If nitrogen was replaced by a hydrogenated ambient, thermal donor formation was largely enhanced. In each case further nucleation was affected. A modification of the precipitation path due to rapid thermal annealing is proposed to be at the origin of the tremendous effect of a prior lamp anneal on the internal gettering process. The classic heterogeneous nucleation of the platelets would be prevented and the precipitation would proceed through a homogeneous path leading to precipitates unable to getter metal impurities.