Dynamic model of the electrode sheaths in symmetrically driven rf discharges

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Abstract
A self-consistent dynamic model for rf sheaths in the frequency range between the ion and electron plasma frequencies is developed and solved for arbitrary collision parameters and arbitrary rf sheath voltages. For floating dc sheaths with no rf voltage, and for collisionless and highly collisional rf sheaths at high rf voltages, the obtained solutions for the dc sheath voltage and the capacitive sheath width converge to the known limits. However, for rf voltages of tens and hundreds of volts, usually encountered in rf discharge applications, our results differ from those obtained using high voltage approximations and are in good agreement with the experiment. The found relations between the sheath characteristics show that the rf sheath capacitance and the equivalent sheath resistance, corresponding to ion acceleration losses, are practically independent of the rf voltage and the discharge current.