The role of defect excesses in damage formation in Si during ion implantation at elevated temperature

New insight into damage formation in Si(100) during self-ion irradiation is gained from elevated temperature implant (up to 450°C) studies and dual implants. Ion-induced damage is shown to bifurcate at high temperatures into two distinctly different layers; a heavily dislocated region near the ion range, and a shallower layer which is dislocation-free but contains vacancy-type clusters. A model to account for these defects and their distribution is presented. The formation of a layer with a preponderance of vacancy clusters provides opportunities to study aspects of damage growth which have, heretofore, been impossible. Samples in which a vacancy-rich region had been formed were used as starting substrates for implantation to investigate ion-solid interaction phenomena. The preexisting vacancy clusters are shown to provide recombination sites for subsequently implanted ions. Recombination at 450°C is sufficiently effective that no additional damage is formed by direct implantation into the vacancy-rich region, at least up to the dose that can be accommodated by the vacancy distribution. This result establishes the role of defect excesses in the formation of ion-induced damage, even at temperatures approaching ambient.