The present invention generally relates to an electrostatic chuck assembly for uniformly processing a wafer in a semiconductor wafer processing process, more particularly to prevent a byproduct formed from leakage of wafer processing materials from depositing between a wafer and the electrostatic chuck assembly.The electrostatic chuck assembly has a wafer holding member for holding a wafer; a shadow ring in engagement with the wafer holding member; and an insert ring disposed between the shadow ring and the wafer holding member.The wafer holding member has a wafer mounting surface and may preferably have a conical head having a tapered peripheral wall and a cylindrical portion. Alternatively, the wafer holding member is cylindrical and extends downwardly from the wafer mounting surface. The insert ring has an inner wall for sealably engaging the wafer holding member and preferably, is removable to allow for easy cleaning of the electrostatic chuck assembly.