The vacancy mechanism of dopant diffusion in silicon was investigated at the microscopic level. The concentration dependence of the dopant diffusion constant in the high-concentration regime was simulated using Monte Carlo methods plus an atomistic model of clustering and precipitation. The simulation took account of the microscopic forces between particles (dopant atoms, vacancies) in a quantitative manner. Because sufficiently accurate data on the binding strength and shape of the interaction potentials were unavailable, various model approaches to these interactions were analyzed. Purely attractive forces between dopants and vacancies were considered. It was found that, using this approach, it was not possible to fit the experimental results. Models with repulsive dopant-dopant potentials of Coulomb shape, together with attractive dopant-vacancy forces, were also found to give unrealistic results. A good fit to experimental data was obtained by assuming a non-binding dopant-vacancy interaction that increased the mobility of the vacancy only in the neighborhood of a dopant.

Atomistic Modeling of High-Concentration Effects of Impurity Diffusion in Silicon. S.List, H.Ryssel: Journal of Applied Physics, 1998, 83[12], 7595-607