Capacitive and resistive double sheath model in an asymmetric radio frequency plasma discharge

Abstract

The double asymmetric probe model presented here solves the rectified rf potential and rf currents in an asymmetric rf discharge as a function of the electrode surface ratio S1/S2, the rf potential compared to the floating potential, and the sheath capacitances on both sides of the discharge. It is demonstrated that this asymmetric unmagnetized model can be applied to a magnetized double probe one in which the asymmetry arises from the anisotropy between parallel and perpendicular currents. Asymptotic solutions for highly asymmetric discharges yield a dc saturation current on the rf electrode equal to −Isat/2 for low sheath capacitance and −Isat for high sheath capacitance. The transition capacitance between “low” and “high” is defined as C0. A solution of the rf averaged current and rectified potential as a function of the surface ratio and the rf potential are also proposed for each regime. These analytical solutions are confirmed by the full numerical model taking into account the generator resistance and the plasma conductivity.