A vacuum processing chamber with walls defining a cavity for processing a substrate. The processing chamber includes a substrate support for supporting a substrate being processed in the cavity, a shadow frame for preventing processing of a perimeter portion of the substrate, and a shadow frame support supporting the shadow frame within the cavity. The shadow frame is positionable with a gap between an underside of the shadow frame and an upper surface of the substrate. At least one conductive element insulated from the walls and establishes a conductive path from the shadow frame to outside the cavity. The conductive path may be used to discharge charge from the shadow frame at a rate sufficient to prevent a voltage differential from accumulating between the shadow frame and the substrate which would cause arcing therebetween, or to apply a bias voltage to the shadow frame sufficient to attract particles to reduce contamination of the substrate.