Backside gas quick dump apparatus for a semiconductor wafer processing system

Apparatus for retaining a workpiece in a semiconductor wafer processing system. The apparatus has a collector positioned between an electrostatic chuck pedestal and the floor of the processing chamber. The collector has inlet and exhaust control valves connected to inlet and exhaust ports for providing and expelling a backside heat transfer gas (e.g., Helium). Heat transfer exhaust cavities in the collector are connected to the exhaust port to rapidly draw the gas off the backside of the wafer. Additionally, control of the heat transfer gas layer uniformity during processing is achieved by opening and closing the valves to the inlet and exhaust ports as required.