A model for P diffusion during rapid thermal processing was developed. It was based upon observations of an enhanced diffusivity in the presence of a relatively high concentration of interstitial dopant. The effect of an amorphous to crystalline transformation, upon the initial point defect concentration, was considered for high-dose implantation. A pair of coupled non-linear partial differential equations for vacancy and self-interstitial assisted P diffusion was solved numerically. From implantation profile data, it was estimated that the P diffusion behavior could be described by the expression:

D(cm2/s) = 1.41 x 10-5 exp[-1.8(eV)/kT]

It was concluded that the so-called anomalous diffusion of P during rapid thermal annealing was due to the presence of a proportion of interstitial dopant which could diffuse relatively quickly, via a self-interstitial assisted mechanism. The above proportion depended upon the implantation conditions and the crystallographic transformations which the lattice underwent during annealing.

L.Nanu, A.G.R.Evans: Semiconductor Science and Technology, 1989, 4[9], 711-4