Model for boron diffusion in Si at high concentrations

Modeling of the diffusion of high-concentration, implanted B in Si is done. The movement of boron at low concentrations is generally thought to be controlled by the interaction of substitutional boron with the singly-charged donor vacancy. Profiles determined by this model are shown to be substantially different than diffusion profiles in Si implanted with either B+ or BF2+ ions at high dose. A two-stream model, in which boron movement is dominated by a dissociative process involving both interstitial and substitutional diffusion, is found to be in good agreement with the data. Also, it is shown that the use of rapid thermal annealing to form shallow p+ junctions offers a potential advantage over conventional annealing with regards to the dissociative mechanism. (orig.)