Development of a high-density radio frequency plasma source with a ring-shaped trench hollow electrode for dry processing

Abstract

A high-density plasma driven by a capacitive discharge with a radio frequency of 13.56 MHz has been developed using a powered electrode with a ring-shaped trench for dry processing. It was found that a hollow cathode discharge was produced in the trench at a wide range of pressures from 10 to 400 mTorr. In order to satisfy the hollow cathode discharge, it was clarified that the trench width was twice as long as the sheath thickness formed in the trench experimentally. It became clear that a wider trench width easily produced the hollow cathode discharge under lower pressure conditions. A maximum plasma density of 1011 cm−3 was attained at Ar gas pressures of 100–350 mTorr and/or an input power density of 0.64 W cm−2. It was indicated that the radial profile of plasma density had a peak near the ring-shaped trenches and was uniform inside the ring-shaped trench.