Ion energy distributions versus frequency and ion mass at the rf-biased electrode in an inductively driven discharge

In this article, we present ion energy distributions (IEDs) at a rf-biased surface as a function of driving frequency and ion mass. The experiments were carried out in high-density inductively coupled rare-gas (Ne,Ar,Xe) plasmas. Our quadrupole mass and cylindrical-mirror energy analyzer sampled ions incident on a rf-biased pinhole located in the center of the wafer chuck. The electron density, electron temperature, and plasma and chuck potential oscillations were measured, and they provided inputs to numerical models used to predict IEDs, which were shown to closely match our experimental results under certain conditions. For a given driving frequency, heavier ions showed narrower IEDs and, for a given ion mass, the IED became narrower and shifted to a higher mean energy with increased driving frequency, in agreement with calculations.