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

A collisionless hybrid simulation (particle ions and Boltzmann electrons) has been used to study sheath and ion dynamics following the application of a large negative voltage pulse to three different ring-shaped targets: a thin ring, a thick ring, and an outer bearing race. The influence of a coaxial auxiliary electrode has also been investigated. The normalized potential, ion density, incident dose and accumulated impact energy on the target surfaces are presented. Three classes of ion trajectories are identified: those that impact the target directly, those that pass through the ring and impact the target, and those that pass through the ring and back into the ambient plasma. Implantation of the top and outer surfaces of the thick ring/bearing are influenced by the use of the auxiliary electrode because it significantly reduces the number of ions passing through the ring. The implications of this work for the plasma immersion ion implantation process are discussed.