New model for boron diffusion in silicon

A new model for boron diffusion in silicon is proposed in which it is assumed that the dominant diffusing species is a neutral boron-vacancy pair (B−V+). Analysis of the model shows that when CB is not the dominant species, the solution of the diffusion equation for constant surface concentration is a complementary error function. When CB is the dominant species during at least part of the diffusion, the diffusion equation must be solved numerically. It is shown that in this latter case, the variation of positively charged vacancy concentration with Fermi level causes the boron diffusivity to appear to be concentration dependent.