Improving the uniformity of RF-plasma density by a humped variable-gap spiral antenna

This paper develops a humped spiral antenna of top inductively coupled plasma with variable gap. Comparing with planar spiral antennae, it investigates the performance of humped spiral antennae in the calculated electromagnetic configurations and experimental results. It finds that the humped antenna has the improved uniformity of plasma density in the radial direction and the decreased electron temperature in the top inductively coupled plasma. By experimental and theoretical analyses, the plasma performance in the case of humped antennae is considered to be the combined results of the uniform electromagnetic configurations and the depressed capacitively coupling effect. (fluids, plasmas and electric discharges)