Hybrid simulation of sheath and ion dynamics of plasma implantation into ring-shaped targets

A collisionless hybrid simulation (particle ions and Boltzmann electrons) h as been used to study sheath and ion dynamics following the application of a large negative voltage pulse to three different ring-shaped targets: a th in ring, a thick ring, and an outer bearing race. The influence of a coaxia l auxiliary electrode has also been investigated. The normalized potential, ion density, incident dose and accumulated impact energy on the target sur faces are presented. Three classes of ion trajectories are identified: thos e that impact the target directly, those that pass through the ring and imp act the target, and those that pass through the ring and back into the ambi ent plasma. Implantation of the top and outer surfaces of the thick ring/be aring are influenced by the use of the auxiliary electrode because it signi ficantly reduces the number of ions passing through the ring. The implicati ons of this work for the plasma immersion ion implantation process are disc ussed.