Energy-resolved mass spectrometry and Monte Carlo simulation of atomic transport in magnetron sputtering

Abstract

Here we report the energy distributions of ions measured by an energy-resolved mass spectrometer during magnetron sputtering of Cu in Ar. The effects of the discharge power on the distributions are described. Both Cu+ and Ar+ ions exhibit non-equilibrium energy distributions with a main maximum (corresponding to thermalized species) and a high-energy tail, with energies ranging up to about 50 eV. The experimental data are compared with the results of a direct simulation Monte Carlo computer simulation. The elastic collisions of neutral species are calculated in a quasi three-dimensional geometry with two-dimensional cells and a featureless third dimension. The collision cross-section and scattering angles are calculated using the Biersack–Ziegler interatomic potential. The Sigmund–Thompson distribution is used for the sputtered atoms. The calculated energy distributions of Cu and Ar atoms as a function of discharge power are correlated with the experimental data. Momentum transfer in elastic collisions with the sputtered particles may be the main effect contributing to the formation of the non-equilibrium energy distribution of the gas molecules. The calculated average energy of the Ar atoms increases proportionally to the discharge current, and reaches values of above 1000 K.