PHOSPHORUS-ENHANCED DIFFUSION OF ANTIMONY DUE TO GENERATION OF SELF-INTERSTITIALS

In a series of experiments, the influence of phosphorus diffusion at h igh concentrations on the diffusion of an antimony marker layer was in vestigated. The marker layer was separated from the surface by a 4 mu m layer of epitaxially grown silicon. To reduce the effects of implant ation enhancement and phosphorus precipitation on the diffusion of the antimony marker layer, the phosphorus was implanted into a polysilico n layer deposited on top of the single-crystalline substrate. It was f ound that the diffusion of the antimony marker layer is already reduce d by the epilayer. From these diffusion coefficients, upper limits for the fractional diffusivity of antimony were derived. In contrast to p revious investigations, the diffusion of the antimony marker layer was found to be enhanced below regions where phosphorus was implanted. A comparison of diffusion in FZ and CZ samples shows that this enhanced diffusion of antimony can be explained only by an injection; of self-i nterstitials from the phosphorus-doped region. Since the polysilicon l ayer was found to recrystallize, this self-interstitial injection can be the result of phosphorus diffusing mainly via self-interstitials, p hosphorus precipitation, or both. Using Boltzmann-Matano analysis and antimony diffusivity data, the fractional diffusivity of phosphorus vi a self-interstitials was estimated to be lower than 0.71 at 950 degree s C. Possible sources of error in this estimation are discussed. (C) 1 995 American Institute of Physics.