It was recalled that co-implantation of carbon in a concentration range which was comparable to that of boron could suppress B diffusion and result in a box-like B profile. Substitutional C atoms could capture excess self-interstitial Si atoms and suppress the diffusion of ion-implanted interstitial-type dopants such as B in silicon. It was confirmed here for the first time that, for wide C and B concentration ranges, the B activation ratio of Si increased or decreased depending upon the concentration of C that was incorporated. The activation ratio of the B activation layer was markedly increased by C incorporation in the case of slight B implantation: 8 x 1019 to 3 x 1020/cm3. This could be attributed to the interaction of C with Si interstitials, and to suppression of the boron Si-interstitial clustering induced by C incorporation. In the case of heavy B implantation (1021/cm3), 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 upon the activation ratio was small.

Contribution of Carbon to Activation and Diffusion of Boron in Silicon. H.Itokawa, Y.Agatsuma, N.Aoki, N.Uchitomi, I.Mizushima: Japanese Journal of Applied Physics, 2010, 49, 04DA06