Embodiments of the present invention generally relates to substrate supports for use in a plasma processing chamber. The substrate supports, which are metallic, have ceramic inserts to prevent arcing between the substrate support and the shadow frame used to protect the edges of the substrate support during processing. In large area substrate processing chambers, the shadow frame may comprise multiple pieces. The individual pieces may be coupled together, but spaced slightly apart by a gap to permit thermal expansion. Ceramic inserts are positioned on the substrate support so that when a shadow frame is positioned adjacent thereto, the ceramic inserts are located adjacent the gaps in the shadow frame. The ceramic inserts adjacent the gap prevent and/or reduce the arcing because the gaps are located over electrically insulating material rather than electrically conductive material.