Ion energy distribution functions in magnetized capacitively coupled RF discharges

摘要

The influence of a spatially inhomogeneous static magnetic field on the characteristics of capacitively coupled radio frequency discharges is investigated. In particular, the focus is placed on the sheath dynamics and the ion energy distribution functions (IEDFs) of ions impinging the electrodes. For this study we employ two different kinetic models. The first is the Particle-in-Cell (PIC) code yapic [1], which takes into account the entire discharge; the second code is the Ensemble-in-Spacetime (EST) model [2] which resolves the plasma boundary sheath only. We make a comparison of the two models by using the sheath voltage and the ion flux through the sheath calculated with PIC as input for EST. [3] We find excellent agreement of the IEDFs calculated with both methods. In addition, good qualitative agreement of the sheath dynamics is observed. However, a quantitative discrepancy between the models can be identified, caused by different collision processes implemented in both models. While it is found that electrons are strongly affected by the applied magnetic field, ions are only indirectly influenced in terms of the asymmetry of the discharge. In addition, we find that EST may be used as an efficient postprocessing tool to obtain the IEDFs even in magnetized cases, in particular if only simplified (i.e., global or fluid-dynamic) models are available.