Low-field helicon discharges

Operation of helicon discharges at magnetic fields B-0 below 100 G is of interest for plasma etching and deposition reactors if high ion Bur can be maintained with reduced field requirements. The theory of coupled helicon and Trivelpiece-Gould modes is summarized for uniform B-0. Initial results from two experiments are reported. The first has a single 5 cm diameter tube with B-0 = 0-100 G injecting plasma into a field-free region. The second contains a two-dimensional array of seven such tubes covering a large area Densities and density profiles are measured for various fields, RF powers and gas pressures. The highest density generally occurs at zero held. Because of the Iron-uniformity in B-0, direct comparison with theory cannot yet be made.