A MODEL FOR BORON SHORT-TIME ANNEALING AFTER ION-IMPLANTATION

A simulation model is proposed for boron diffusion in silicon, which i s especially useful for analyzing the short time annealing process sub sequent to ion implantation. This model takes into account nonequilibr ium diffusion and reactions of point defects and defect-dopant pairs, considering their charge states, and the dopant inactivation by introd ucing a boron clustering reaction. It was assumed that the boron-inter stitial silicon pair(BI) is a dominant diffusion species that contribu tes to the total boron diffusion. A primary model parameter, the bindi ng energy of BI, was determined to reproduce the equilibrium gaseous s ource diffusion data. Using a single set of reasonable parameter value s, the model covers not only the equilibrium diffusion conditions, fro m intrinsic to extrinsic, but also the nonequilibrium post-implantatio n diffusion. Experimental boron distribution profiles could be accurat ely reproduced in terms of transient-enhanced diffusion and incomplete activation. A result, obtained from the analysis using this model, sh owed that the time constant for the BI-dissociation-reaction rules the transient characteristics for the boron diffusion enhancement during post-implantation annealing.