VARIABLE-ENERGY POSITRON BEAM STUDY OF ARSENIC DIFFUSION IN POLYSILICON

The positron beam technique is shown to be a sensitive indicator of th e presence of arsenic within the grain boundaries of poly-silicon. Var iable-energy positron beam and secondary-ion mass spectrometry studies have been performed on As+-implanted pre-amorphized Si samples as a f unction of dose and rapid thermal anneal temperature. Positron trappin g within negatively-charged grain boundaries of the recrystallized pol y-Si is observed, resulting in a similar to 2% elevation in the Dopple r-broadening S lineshape parameter value. Infusion of As+-ions into th e grain boundaries passivates the charge and reduces their specific po sitron-trapping rate.