Basic investigations of an integrated modulator for plasma immersion ion implantation

The replacement of an external high voltage modulator by an integrated plasma based modulator, would considerably reduce the costs of plasma immersion ion implantation equipment. An inherent restriction of the integrated modulator is the limited maximum current. In order to overcome this limitation, detailed investigations are presented on the response of the plasma if electrons are extracted by a large auxiliary anode with special emphasis on the processes near the wall and near the control grid of the modulator. An anode potential of 20 kV results in an increase of the plasma floating potential from −8 V to approximately 60 V, as revealed by probe measurements, so that all electrons leaving the plasma are collected by the anode. Simultaneously a two- to threefold increase of the plasma density is observed.