Spatial distributions of dust particles in plasmas generated by capacitively coupled radiofrequency discharges

Abstract

The transport of particles ('dust') in low-pressure electrical glow discharges is of interest with respect to contamination of semiconductor wafers during plasma etching and deposition. The distribution of dust particles in these reactors is determined by a variety of forces, the most important being electrostatic, viscous ion drag, gravitational, thermophoretic and neutral fluid drag. In this paper we present results from a series of computer models to predict the spatial distribution of dust particles in capacitively coupled electrical glow discharges considering these forces. The results are parametrized over power deposition, gas flow and particle size. We find that the spatial distribution of dust depends on the spatial dependence of the sheaths and plasma potential in bulk plasma which in turn depend upon the electrical topography of the surfaces. Experimentally observed 'dome' and 'ring' distributions of dust particles are computationally reproduced for specific combinations of discharge power particle size and substrate topography.