A process chamber includes a wafer support to mount a wafer to be processed in the process chamber, with the wafer having an annular edge exclusion area. A first electrically grounded ring extends in an annular path radially outward of the edge exclusion area and is electrically isolated from the wafer support. A second electrode is configured with a center area opposite to the wafer support. A second electrically grounded ring extends in an annular path radially outward of the second electrode and the edge exclusion area. The second electrically grounded ring is electrically isolated from the center area. An annular mount section has a DC bias ring, and the DC bias ring opposes the edge exclusion area when the wafer is present. A DC control circuit is provided for applying a DC voltage to the DC bias ring.