Laboratory measurements and optimization of inductively coupled loop antenna plasma sources

Uniform high density plasmas at low neutral species pressure, with high efficiency and low ion bombarding energy can be produced with inductively coupled plasma sources. We describe experimental investigations of several variations on antenna inductive sources, including single-, double- and spiral loop antennae. Experimental data and computer modelling demonstrate the advantages of the spiral loop design over other inductive source geometries. The models also make extrapolation to other designs fairly straightforward. Source performance at a driving frequency of 13.56 MHz as a function of input power, working gas, additional line cusp confinement, neutral species pressure and background magnetic field will be described. Source construction details and some design rules of thumb are also outlined.