Monte Carlo simulation of the variation of a binary alloy film composition due to intrinsic resputtering using different working gases

Abstract

Intrinsic resputtering is inherently associated with the sputtering process. It is caused by energetic neutral particles resulting from primary sputtering events at the target. These energetic particles are target material atoms with energies up to tens of electronvolts and sputter gas neutrals backscattered from the target with energies exceeding 100 eV. To calculate the gas phase transport of energetic particles and the resputtering effects from the vacuum chamber walls and the substrate, we employed the Monte Carlo technique. The yield for each kind of sputtering event (and also the resputtering process) depends on the mass of the impinging particle and the mass and surface binding energy of the sputtered atom. To study the effect of various working gas atoms on the intrinsic resputtering processes, we simulated the deposition of a Cu-Pb film. Cu and Pb atoms have very different surface binding energies and masses. The variation of the working gas influences the energy of the primary sputtered target atoms and the reflected neutrals. Hence the composition of the deposited binary alloy film due to intrinsic resputtering varies with the pressure due to the different energy transfer from the target to the substrate and the surrounding chamber walls. To check the validity of the simulation results, we also performed experiments with an identical geometry with sputtering from a Cu-2.05at.%Pb target using He, Ne, Ar and Xe as the sputter gases.