Ion plating processes: Design criteria and system optimization

Important factors to be considered in the design and optimization of ionization-assisted physical vapour deposition systems include (i) non-uniform plasma effects caused by ionization enhancement, (ii) permissible mixing of different sized substrates and (iii) coating thickness uniformity. We have shown that plasma intensification with an electron emitter can impart non-uniform effects which are primarily related to the mean free path for electron impact ionization. Secondly, the influence of cathode fall distance on factor (ii) is highlighted by comparing sputter weight loss measurements with theoretical predictions. Finally, coating uniformity in terms of front-to-back thickness ratios is shown to follow a hyperbolic function while the absolute thickness can be expressed as an inverse power function of the source-to-substrate distance.