Evolution of Defect and Impurity Profile During High Dose Co Implantation into Si at Elevated Temperatures

Abstract

ABSTRACTȥ111Ɂ -Si was implanted with 250 keV Co ions at a target temperature of 350°C. The ion dose was varied between 1×1014 cm-2 and 2×1017 cm-2 . The evolution of the defect and impurity profile was investigated by Rutherford Backscattering Spectrometry (RBS), channeling and transmission electron microscopy (TEM).Up to a dose of 1 × 1015 Co cm-2 no defects can be detected. At higher Co doses, we find correlated defects in the center of the Co distribution and point defects in the region below. Moreover, damage accumulation at the surface is observed. The concentration of defects increases with increasing ion dose and reaches its level of saturation at a dose of 2 × 1016 cm-2.The Co profiles of samples implanted at 350°C differ considerably from the Gaussian shape. The near surface and the back flank are parts of Gaussian distributions. However, the standard deviation of the near surface flank is always smaller than that of the back flank. Moreover, the distributions show tails into the substrate at depths > 320 nm. This proves that radiation damage acts as an effective center for the nucleation of CoSi2.During annealing we find a redistribution of Co towards the defective regions for Co doses between 1 × 1016 cm-2 and 5× 1016 cm-2.