Apparatus for improving wafer and chuck edge protection

Apparatus for retaining a wafer having improved wafer and chuck edge protection, contains an protection ring that circumscribes a pedestal and is biased to be in constant contact with the backside of the wafer. A biasing element uniformly biases the protection ring into contact with the circumferential edge of the wafer. The protection ring has an annular plan form that circumscribes an electrostatic chuck for retaining the wafer in a stationery position. Vertical travel of the ring is restricted by a hard stop that is formed by a portion of a focus ring which overhangs the protection ring. After a wafer is placed upon the chuck and the chucking force enabled, the chucking force easily overcomes the bias force upon the protection ring and the wafer rests upon the chuck support surface. The protection ring contacts the backside of the wafer to ensure that pedestal and electrostatic chuck are not exposed to the plasma and, when a silicon protection ring is used, the effective area of the wafer is extended beyond the physical dimensions of the wafer to facilitate a more uniform plasma distribution over the wafer.