Reduction of Residual Charge in Surface-Neutralization-Based Neutral Beams

Hyperthennal-neutral beams have been proposed as a charge-free alternative to plasmas in select processing steps. Existing prototype sources include three generic types: gas-dynamic, ion-neutral-charge-exchange and ion-surfaceneutralization beam sources. We find that in surface-neutralization type sources, which have the highest flw residual current can still flow to the substrate. However, this charged particle flux is several orders of magnitude smaller than the hyperthermal-neutral flux. Here we discuss the source of this residual current and methods for further reductions.