Abstract: A gas distribution apparatus delivers a coolant gas, such as helium, to an upper surface of a chuck for controlling a temperature of a wafer placed on the chuck. The gas distribution apparatus allows first and second zones, such as an inner zone and an outer zone of the chuck, to be supplied with a coolant gas at different pressures for control of the temperature across the wafer. The gas distribution apparatus includes a pressure and flow control system for supplying the coolant gas at selected pressures and bleed lines which provide the dual function of allowing rapid evacuation of the inner and outer zones and preventing excess pressure from one zone from migrating to another zone.

Abstract: A composite release sleeve includes a first cylindrical sleeve of a non-metallic material, and a second cylindrical sleeve of a metallic material. The composite release sleeve enables translation movement of a bearing such as a clutch release bearing, upon a guide element such as an input shaft. Preferably, the first cylindrical sleeve material is a polymer composite having a molded-in second cylindrical sleeve such as a bronze bushing. An integral flange extending outwardly from one end of the first cylindrical sleeve transfers the axial motion of the release sleeve to the clutch assembly. The first cylindrical sleeve further includes an integrally molded cavity which serves as a lubrication reservoir to reduce friction and facilitate slidable movement of the composite release sleeve along the input shaft.