The diffusion of Sb into Si, and its dependence upon the Fermi-level position and the structure of lattice defects, was investigated by implanting high (2 x 1016 or 5 x 1016/cm2) doses of Sb ions. The donor concentration was strongly increased by subsequent pulsed-laser annealing. For comparison, laser annealing of samples which were co-implanted with the same doses of Sb and B was carried out in order to obtain strong electrical compensation. The diffusion heat treatment of Sb- and Sb+B-implanted wafers was performed at a relatively low temperature (600C, 1h). Contrary to the extrapolated predictions of previous work, a significant shift in the dopant concentration profiles was observed, as well as the formation of Sb precipitates, Sb-vacancies and/or Sb-B pairing. In order to explain the diffusivity data, a diffusion coefficient had to be assumed which was independent of the dopant concentration and was 7 orders of magnitude higher than that previously determined. This suggested that the increased Sb diffusivity was not due mainly to the Fermi-level position. The huge increase in the Sb diffusivity was attributed to the defects (twins, dislocations, rod-like defects, precipitates, dopant complexes) which were revealed by extended X-ray-absorption fine-structure, Rutherford back-scattering spectrometry or channelling, and transmission electron microscopic techniques. An anomalously high tensile strain in the samples indicated a marked incorporation of vacancies. These defects were also held to be responsible for a backwards diffusion and an out-diffusion of the dopant which occurred during thermal annealing of most of the samples.

A.Armigliato, F.Romanato, A.Drigo, A.Carnera, C.Brizard, J.R.Regnard, J.L.Allain: Physical Review B, 1995, 52[3], 1859-73