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 und er nitrogen or hydrogenated ambients on thermal donor formation and on the further oxygen nucleation step were studied. A rapid thermal anne aling at 1200 degrees 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 n ucleation was affected. A modification of the precipitation path due t o rapid thermal annealing is proposed to be at the origin of the treme ndous effect of a prior lamp anneal on the internal gettering process. The classic heterogeneous nucleation of the platelets would be preven ted and the precipitation would proceed through a homogeneous path lea ding to precipitates unable to getter metal impurities.