A COMPARISON OF RF ELECTRODE SHEATH MODELS

Analytic expressions have been found from different time-averaged and dynamic models for the electrode sheath width in a capacitively driven RF discharge. The sheath widths predicted from all the models under c onsideration are shown to practically coincide if they are expressed i n terms of dc sheath voltage and ion current to the RF electrode. Howe ver, these models have fundamental differences in their RF discharge s caling laws that result in different theoretical predictions for RF di scharge electrical characteristics. Analytic expressions for the sheat h width with arbitrary collisionality at moderate RF voltages are foun d to be in good agreement with experimental measurements made over a w ide range of discharge voltage and gas pressure.