Heating effects in ionization-assisted processes

Ionization-assisted processes, such as ion plating, ion nitriding and plasma-assisted chemical vapour deposition, all impart a discharge heating effect on the workpiece. Increased levels of ionization efficiency are being specified with the consequential risk of substrate deterioration due to overheating. In this paper a thermodynamic model which can predict the substrate temperature resulting from different ionization conditions is outlined. A particularly useful feature is that it includes a provision for the variation in workpiece emissivity with increasing temperature. The benefit to laboratories and producers in the field will bein the optimization of discharge conditions through the identification of limiting current density levels and the relative importance of the various heat sources and sinks present.