The diffusion of Sb in samples with, or without, a 20nm-thick molecular beam allotaxial CoSi2 top-layer was investigated during annealing and oxidation by using doping superlattices. The latter were grown by means of molecular beam epitaxy, and consisted of 6 spikes with peak concentrations of about 1019/cm3, with peak centres that were spaced 100nm apart. The shallowest spike was capped with 100nm of Si, followed by 20nm of CoSi2. Annealing in pure N2 and oxidation in pure O2 were carried out at 800 to 1200C. The concentration depth-profiles were measured by means of secondary ion mass spectrometry. The results showed that dopant diffusion was markedly different with, as compared to without, the CoSi2 layer. In the latter specimens, oxidation-retarded diffusion of Sb was observed. However, the effect of CoSi2 layers was to enhance Sb diffusion (table 34). The Sb diffusivity was enhanced by a factor of 2 with respect to thermal diffusivity, and by about a factor of 5 when compared with the CoSi2-free case.

Effect of an Epitaxial CoSi2 Layer on Diffusion of B and Sb in Si during Annealing and Oxidation A.K.Tyagi, L.Kappius, U.Breuer, H.L.Bay, J.S.Becker, S.Mantl, H.J.Dietze: Journal of Applied Physics, 1999, 85[11], 7639-45. See also: Fresenius’ Journal of Analytical Chemistry, 1999, 365[1-3], 282-5