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 irradiati on is gained from elevated temperature implant (up to 450 degrees C) s tudies and dual implants. Ion-induced damage is shown to bifurcate at high temperatures into two distinctly different layers; a heavily disl ocated region near the ion range, and a shallower layer which is dislo cation-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 imposs ible. Samples in which a vacancy-rich region had been formed were used as starting substrates for implantation to investigate ion-solid inte raction phenomena. The preexisting vacancy clusters are shown to provi de recombination sites for subsequently implanted ions. Recombination at 450 degrees C is sufficiently effective that no additional damage i s 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 o f ion-induced damage, even at temperatures approaching ambient. (C) 19 98 Elsevier Science S.A. All rights reserved.