Measurement of energy-resolved ion angular distribution in a dual-frequency capacitively coupled argon plasma

Abstract An energy-resolved angular distribution measurement of ions impinging on a biased radiofrequency (RF) electrode was performed in a dual-frequency capacitively coupled plasma. The ion angular distribution (IAD) was measured using a microchannel plate (MCP) in a drift chamber directly connected to the RF electrode. Using deflector plates with pulse-modulated voltage, IADs with various incident energies for Ar were successfully observed using a time-of-flight technique. Images measured using the MCP originated from the spatially overlapped IADs of various incident energies. Through image reconstruction assisted by a gradient descent method, the images were separated into energy-resolved IADs. The angular widths (AW) of the Ar ions were evaluated as a function of the incident energy, showing a monotonic decrease in AW as the energy increased. From the energy dependence of the AW, the Ar ion temperature was evaluated as 0.044 eV. The result demonstrated the validity of the energy-resolved IAD measurement using this method.