Monte Carlo numerical analysis of target erosion and film growth in a three-dimensional sputtering chamber

Abstract

A combination of two mathematical models for three-dimensional Monte Carlo particle simulation of a low pressure sputtering environment is proposed. One is intended for the simulation of a discharge gas flow, and the other for the sputtered atom transport. The combination is used to characterize target erosion and film growth. The models are refined with recourse to experimental measurements made in a practical sputtering apparatus (SPF-210 AS, ANELVA Ltd.) over the range of operating pressures and flow rates of 0.3–10 Pa and 0.5–5 sccm, respectively. A considerable number of numerical analyses are done to find possible reasons for the measured nonuniformity of target erosion and film growth rate distributions. Simulation results show that under the operating and design conditions treated here the nonuniformity of gas flow field appears to be too weak to explain the experimental data. Film growth rates simulated for measured erosion rates show a good agreement with the experimental data for the various operating pressures above. Important features of the present simulation are the inclination of the angular distribution of sputtered atoms, and taking into consideration reemission of sputtered atoms deposited onto the target. The inclination of angular distribution results from the oblique ion incidence onto the target surface. The existence of highly eroded etch track along the target edge is shown to be correlated with the greater sputtering yield for the oblique ion incidence near the edge. Axial asymmetry of the erosion and growth rate distributions may be due to the asymmetry of the electric field lines at the periphery of the target, which leads to a nonuniform incidence angle along the edge. In contrast to erosion and growth rates, the redeposition rate of sputtered atoms onto the target is found to increase considerably with pressure.