an apparatus for providing an electrical bias to a substrate in a processing system is described . the apparatus generally includes a conductive annular body defining a central opening . the conductive annular body may have a substrate seating surface adapted to receive the substrate and a plurality of scallops formed on a surface opposing the substrate seating surface . a plurality of electrical contacts may be formed on the substrate seating surface opposite the plurality of scallops . the electrical contacts may be adapted to engage a plating surface of the substrate .