A method of processing a semiconductor workpiece includes placing a back surface of the workpiece on a workpiece support in a chamber so that the front surface of the workpiece faces into the chamber for processing, and the back surface is in fluid communication with a back region having an associated back gas pressure. The method further includes performing a workpiece processing step at a first chamber pressure Pc1 and a first back pressure Pb1, wherein Pc1 and Pb1 give rise to a pressure differential, Pb1−Pc1, and performing a workpiece cooling step at a second chamber pressure Pc2 and a second back pressure Pb2, wherein Pc2 and Pb2 are higher than Pc1 and Pb1, respectively.