The migration of B and P in heavily doped layers (extrinsic at the process temperature) was studied in order to obtain information on Si interstitial concentrations in heavily doped layers. The diffusion of both dopants in n-type and p-type iso-concentration structures was measured for 2 surfaces. One surface was passivated with low-pressure chemical vapor deposited oxides and nitrides, and the other was a growing thermal oxide. The degree of oxidation-enhanced diffusion was measured for both dopants and was found to be smaller than for the same annealing treatments under lightly doped conditions (intrinsic at process temperatures). The P data were analyzed, and effective Si interstitial energy levels for modelling the diffusion of heavily doped layers were obtained. The diffusion of P was also studied in iso-concentration structures, with and without a lightly doped epitaxial layer at the surface, in order to determine the effect of doping at the Si/SiO2 interface upon diffusivity enhancement. It was found that samples with epitaxial layers exhibited greater enhancements as compared with samples that did not. The results were explained in terms of charged interstitial drift in the electric field which was set up by ionized dopant atoms, and a resultant increase in the flux of interstitials away from the oxidizing interface.

D.J.Roth, J.D.Plummer: Journal of the Electrochemical Society, 1994, 141[4], 1074-81