Plasma Molding over Surface Topography

A two-dimensional fluid/Monte Carlo simulation model was developed to study plasma “molding" over surface topography. The plasma sheath evolution and potential distribution over the surface were predicted with a self consistent fluid simulation. The trajectories of ions and energetic neutrals were then followed with a Monte Carlo simulation. In this paper, energy and angular distributions of ions and energetic neutrals bombarding an otherwise planar target with a step are reported. As one approaches the step, the ion flux decreases and the ion impact angle increases drastically. For a time invariant sheath (DC case), the ion energy distributions (IED) remain relatively unaffected. When the plasma sheath oscillates at radio frequencies, the IED narrows, while the ion angular distribution becomes broader as one approaches the step. The energetic neutral flux is found to be significant near the vertical step wall. The simulation results are in good agreement with experimental data.