Embodiments of the present invention generally relate to an apparatus for reducing arcing during thick film deposition in a plasma process chamber. In one embodiment, an edge ring including an inner edge diameter that is about 0.28 inches to about 0.38 inches larger than an outer diameter of a substrate is utilized when depositing a thick (greater than two microns) layer on the substrate. The layer may be a dielectric layer, such as a carbon hard mask layer, for example an amorphous carbon layer. With the 0.14 inches to 0.19 inches gap between the outer edge of substrate and the inner edge of the edge ring during the deposition of the thick layer, substrate support surface arcing is reduced while the layer thickness uniformity is maintained.