A system for implanting a substrate. The system includes a substrate holder disposed within a process chamber of the system and coupled to ground. The system also includes an electrode disposed within the process chamber and coupled to a power source, the power source configured to supply voltage to the electrode as an unbalanced voltage pulse train, wherein a negative peak voltage during a negative voltage pulse period of the unbalanced voltage pulse train is higher than a positive peak voltage during a positive voltage pulse period of the unbalanced pulse train. The system further includes a movable mask, wherein the movable mask is configured to move between a first position proximate the substrate holder, and a second position proximate the driven electrode.