[Application] A control apparatus for plasma immersion ion implantation of a dielectric substrate which includes an electrode disposed above a generated plasma in a plasma chamber. The electrode is biased with negative voltage pulses at a potential that is higher than a potential of a substrate or cathode configured to receive ion implantation. The electrode is more negative to give the electrons generated as secondary electrons from the electrode sufficient energy to overcome the negative voltage of the high voltage sheath around the substrate thereby reaching the substrate. These electrons are accelerated toward the substrate to neutralize charge build-up on the substrate.