Structured ion energy distribution in radio frequency glow-discharge systems

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Abstract
The energy distribution of ions incident on the cathode (smaller electrode) in a capacitively coupled asymmetric rf discharge was measured for different process parameters. It was found that the ion energy distribution exhibits a characteristic series of peaks, which are explained by the high-frequency modulation of the sheath potential combined with charge exchange in the cathode sheath. A parametric model of the ion transport through the sheath is presented showing that the position of the peaks in the ion energy distribution depends only on a discharge scaling parameter and the spatial variation of the electric field ε(x) across the sheath region. Good agreement between theoretical and experimental ion energy distributions in an argon discharge is obtained for an electric field variation ε(x)∼xν with ν in the range 0.55–0.7.