Characterization of a side-type ferrite inductively coupled plasma source for large-scale processing

Abstract

A new type of inductively coupled plasma (ICP) utilizing an array of auxiliary discharges enhanced with ferromagnetic cores and placed at the chamber side is developed and characterized over a wide range of discharge conditions. The ICP electrical and plasma characteristics are measured over a wide range of discharge powers and argon gas pressures. It is shown that at 400 kHz driving frequency the antenna power factor of this ICP is close to 1, so the antenna voltage and current are much lower than those in a conventional ICP at similar rf power. Due to low driving frequency and low antenna voltage, the capacitive coupling in the ICP mode is practically eliminated, while due to enhanced ferromagnetic core coupling, the power transfer efficiency is higher than 95% at an rf power larger than 0.5 kW. Langmuir probe measurements show that the radial plasma non-uniformity over 300 mm can be less than 3%. This plasma source is expected to be suitable for large-scale plasma processing.