The effect of the boron doping level on the thermal behavior of end-of-range defects in silicon

The effect of the doping level on the formation and growth of end-of-range (EOR) defects is studied. Transmission electron microscopy observations have been performed on boron doped Si wafers (from 1015 to 1020 atom3) preamorphized with germanium and subjected to rapid thermal annealing. When increasing the doping level up to a few 1018 atom3, a delay in the coarsening process encountered by the loops is observed while above this threshold the EOR defects quickly disappear. These results are interpreted by considering three possibly concomitant phenomena: the formation of boron/Si-interstitial clusters, the gettering of boron at the loop periphery, and a change from the intrinsic to the extrinsic regime for self-diffusion. Moreover, an estimate of the effective trapping efficiency of boron is reached and gives about 1±0.3 Si interstitial per boron atom, a value consistent with the one obtained from studies of B transient enhanced diffusion.