The effects of F upon B diffusion in and out of a Si substrate, during N-ambient high-temperature rapid thermal annealing, were studied. By comparing B-implanted and BF2-implanted substrates, it was shown that F out-diffusion during high-temperature annealing coincided with enhanced B out-diffusion into the oxide, and suppressed B diffusion into the substrate. In particular, it was shown that B diffusion was significantly affected by end-of-range dislocation loop dissociation. The combined effects of end-of-range dislocation loop dissociation and simultaneous F out-diffusion from the bulk could retard B diffusion, during high-temperature rapid thermal annealing. This could occur to such an extent that equivalent, or even shallower junctions, could be formed at high annealing temperatures than at the lower temperatures where end-of-range loops were unaffected. This suggested the existence of optimum annealing conditions.

The Influence of Fluorine on Boron-Enhanced Diffusion in Silicon by BF2+ Implantation through Oxide during High-Temperature Rapid Thermal Anneal. L.Z.Wang, M.S.C.Luo, H.H.Tseng, S.A.Ajuria: Journal of the Electrochemical Society, 1997, 144[11], L298-301