Multiple ion dynamics model for the collisionless rf sheaths and the ion energy distributions at rf-biased electrodes...

With a one-dimensional multiple ion dynamics model, we study characteristics of the collisionless radio-frequency (rf) sheaths in fluorocarbon plasmas and calculate the ion energy distributions impinging on rf-biased electrodes. All the time-dependent terms in the ion fluid equations are included and the relationship between the instantaneous sheath voltage and sheath thickness is determined self-consistently by an equivalent circuit equation. The numerical results show that, due to the existence of multi-ion species, the sheath structure in the present work is different from those of single-ion species plasmas, and multiple peaks appear in the ion energy distributions. It is also shown that some parameters such as the bias frequency, bias power, bulk plasma density, and electron temperature are crucial for determining the shape of the ion energy distribution in multicomponent plasmas.