A phenomenological electronic stopping power model for molecular dynamics and Monte Carlo simulation of ion implantation into silicon

摘要

It is crucial to have a good phenomenological model of electronic stoppingpower for modeling the physics of ion implantation into crystalline silicon. Inthe spirit of the Brandt-Kitagawa effective charge theory, we develop a modelfor electronic stopping power for an ion, which can be factorized into (i) aglobally averaged effective charge taking into account effects of close anddistant collisions by target electrons with the ion, and (ii) a local chargedensity dependent electronic stopping power for a proton. This phenomenologicalmodel is implemented into both molecular dynamics and Monte Carlo simulations.There is only one free parameter in the model, namely, the one electron radiusrs0 for unbound electrons. By fine tuning this parameter, it is shown that themodel can work successfully for both boron and arsenic implants. We report thatthe results of the dopant profile simulation for both species are in excellentagreement with the experimental profiles measured by secondary-ion massspectrometry(SIMS) over a wide range of energies and with different incidentdirections. We point out that the model has wide applicability, for it capturesthe correct physics of electronic stopping in ion implantation. This model alsoprovides a good physically-based damping mechanism for molecular dynamicssimulations in the electronic stopping power regime, as evidenced by thestriking agreement of dopant profiles calculated in our molecular dynamicssimulations with the SIMS data.