Ion energy distributions at a capacitively and directly coupled electrode immersed in a plasma generated by a remote source

Ion energy distributions are investigated in an inductively coupled radio-frequency discharge at low pressures. A Langmuir probe is used to characterize the discharge and a retarding field energy analyzer measures the ion flux and energy distributions impacting a remote rf driven electrode. Comparisons are made between capacitive and direct coupling of the rf bias potential. The effects of ICP power, rf bias voltage (0–75 V amplitude), bias frequency (0.5–20 MHz) and discharge pressure (0.2–1.2 Pa) are presented. Results are shown for Ar, O 2 and Ar–He discharges. A double layer was observed during source characterization measurements in an O 2 discharge; however, the focus of this paper is on the behavior of ions through capacitively and directly coupled plasma sheaths.