Intrinsic resputtering during film deposition investigated by Monte Carlo simulation

Abstract

In sputter deposition intrinsic resputtering is caused by energetic neutral particles which result from the primary sputter events at the target. These energetic particles are target material atoms, known to have energies up to tens of electron volts and sputter gas neutrals backscattered from the target with energies of up to hundreds of electron volts. The yield for each kind of sputter event depends on the mass of the impinging particle and the mass and surface binding energy of the sputtered atom. Therefore, the composition of a binary alloy film with strongly different surface binding energies and masses of the atoms involved in the deposition process varies due to their individual amount of resputter events. To explore the intrinsic resputtering we chose the Cu–Pb system. The gas phase transport of energetic particles from a Cu 2.05 at. % Pb target to a cylindrical substrate and the resputtering effects from the chamber walls as well as the substrate were calculated using the Monte Carlo technique. We observe a Pb concentration of the growing film from zero up to a value six times higher than the target concentration depending on the working gas pressure and the vacuum chamber geometry. Good qualitative agreement between simulations and experiments was observed for several geometries and pressures.