Abstract: A wafer mounting plate for mounting a wafer in a chemical mechanical polishing process and a method for using the wafer mounting plate are disclosed. The novel mounting plate for a silicon wafer is designed to incorporate a concave mounting surface for contacting a wafer with a flexible membrane layer thereinbetween. The wafer mounting plate is further provided with a plurality of apertures therethrough for use as vacuum passageways for picking up a wafer through a perforated or breathable membrane layer. The concave surface of the wafer mounting plate that contacts the wafer substantially eliminates stress concentration problems imposed on the wafer by conventional wafer mounting plates. The present invention novel apparatus therefore not only eliminates the edge defect problem that is normally associated with the conventional mounting plates, but further solves the wafer breakage problem frequently caused by stress concentration imposed on the wafer by a bumper ring.