Sheath potential difference studies in low-pressure high-frequency capacitive RF plasma as a fundamental research for ion energy impinging on the material surface

The equation for time-average sheath potential difference from the plasma bulk to the material surface in the low-pressure high-frequency capacitive RF plasma is derived. On the basis of Lieberman's RF sheath model, the presheath potential difference corresponding to Bohm velocity is combined to sheath inner potential. The relation between total potential difference and parameters, including RF current density, plasma density and sheath electron temperature, is derived and is compared with experimental data of sheath potential difference versus RF current density, which shows agreement. Based on this, the equation for ion average kinetic energy impinging on the material surface is obtained. As RF current density increasing, the average energy grows linearly.