Interstitial diffusion under conditions of trapping of interstitial impurity atoms

The diffusion equation for nonequilibrium interstitial impurity atoms in the form convenient for numerical solution has been obtained. The proposed equation takes into account all different charge states of interstitial atoms and drift of all mobile charged species in the built-in electric field, although only the concentration of the neutral impurity interstitials must be obtained to solve the equation. The absorption of impurity interstitials by immobile sinks, mobile vacancies, and due to the passivation of dopant atoms is also taken into account. The derived effective coefficients that describe diffusion and trapping of impurity interstitials have the following characteristic features: (i) their dependences on the concentration of substitutionally dissolved dopant atoms are smooth and monotone; (ii) these concentration dependences are obtained in the form traditionally used for the approximation of effective diffusivity of substitutionally dissolved dopant atoms in processing-simulation codes.To illustrate the usability and efficiency of the derived equation for simulation of diffusion of nonequilibrium interstitial impurity atoms, the migration of deuterium interstitials in the silicon substrate doped with boron has been simulated. The calculated profile of deuterium concentration in the passivated region agrees well with the experimental data.