An investigation was made of the diffusion and electrical activation of In atoms implanted into Si, using energies ranging from 40 to 360keV, to doses of 5 x 1012 or 5 x 1013/cm2 during rapid thermal processing. The investigation revealed a clear dependence of In out-diffusion and electrical activation upon the implantation depth. For a fixed dose, the electrical activation was found to increase with implantation energy. It was proposed that the data could be explained by considering the balance between the local In concentration and the C background. The occurrence of coupling between the C present in the substrate and the implanted In, depending upon the C/In ratio, could give rise to a significant formation of C–In complexes. Such complexes played a role in the enhanced electrical activation, due to the shallower level which they introduced into the Si band-gap (Ev + 0.111eV), with respect to the rather deep level (Ev + 0.156eV) of In alone. The interaction of In atoms with the C background within the Si substrate was therefore identified as being the most likely origin of this behavior. The effect of In and C co-implantation was also studied, in order to investigate the key role played by C in the increase of electrical activation. A large increase in electrical activation was detected in co-implanted samples, up to a factor of about 8, after annealing at 900C. However, C precipitation occurred at 1100C, and had dramatic effects upon the carrier concentration; that fell by some 2 orders of magnitude. This limited the maximum thermal budget that could be used for In activation in C co-implanted material.

Diffusion and Electrical Activation of Indium in Silicon. S.Scalese, M.Italia, A.La Magna, G.Mannino, V.Privitera, M.Bersani, D.Giubertoni, M.Barozzi, S.Solmi, P.Pichler: Journal of Applied Physics, 2003, 93[12], 9773-82