MODELING THE PRESSURE-DEPENDENCE OF DC BIAS VOLTAGE IN ASYMMETRIC, CAPACITIVE RF SHEATHS

A semianalytical model for capacitively coupled radio frequency (RF) s heaths of asymmetric (unequal electrode area) systems has been develop ed, It can be applied in the high-frequency (omega > omega(pi)) regime at different pressures, An analytical approximation to the pressure-d ependent ion density profile is used. The time-varying electric field and potential within the sheath are obtained by solving Poisson's equa tion. The current balance and zero net de current conditions are appli ed to solve for the RF sheath parameters and de bias voltage. The de v oltage ratio between the powered and grounded electrode sheaths increa ses as the pressure decreases, which results in a larger de bias volta ge at lower pressures.