Contribution of Carbon to Activation and Diffusion of Boron in Silicon

Abstract

It is well-known that the coimplantation of carbon (C) in a concentration range comparable to the range of boron (B) concentrations could suppress B diffusion, resulting in a boxlike B profile. Substitutional C atoms can capture excess self-interstitial Si atoms and suppress the diffusion of ion-implanted intersitial-type dopants such as B in silicon (Si). However, the effect of C on activation properties in wide C and B concentration ranges has not been sufficiently investigated. In this work, in the experiment in wide C and B concentration ranges, it was clarified for the first time that the B activation ratio of Si increases or decreases varies depending on the concentration of C incorporated. The activation ratio of the B activation layer was increased markedly by C incorporation in the case of light B implantation such as in the concentration range of 8×1019 to 3×1020 cm-3. This might be attributed to the interaction of C with Si interstitials and the suppression of the boron Si-interstitial clustering induced by C incorporation. In contrast, in the case of heavy B implantation such as at a 1×1021 cm-3 concentration, the activation ratio was decreased slightly by C incorporation. When stable B-containing clusters and precipitates were formed at high B concentrations, the effect of C incorporation on activation ratio was considered to be small.