Insulator surface charging and dissipation during plasma immersion ion implantation using a thin conductive surface film

Abstract

Plasma immersion ion implantation of insulating materials is inherently problematic due to charge accumulation on the insulator surface. Surface charge can be removed by the application of an ultrathin conductive film, which is essentially transparent to the incident ions. The minimum thickness of the film is determined by its capability to effectively conduct away the implanted charge. We present a model for charge accumulation on insulators during plasma immersion ion implantation and use this to study the plasma sheath width and voltage, with and without an ultrathin metal film. Charge accumulation occurs more quickly when the plasma has a directed velocity greater than the Bohm velocity, which is the case for a cathodic arc plasma. We show that for both cases the effectiveness of plasma immersion ion implantation is improved with the application of an ultrathin conductive film.