Abstract: A method and system for fabricating a device on a substrate with a process gas, such as with chemical vapor deposition. A reaction chamber and support chuck cooperate to form a low conductance configuration for axisymetric process gas flow over the substrate and to form a high conductance configuration for enhanced evacuation of residual process gas from the reaction chamber upon completion of the process. A dual conductance chuck has an indented region that aligns with the exhaust port of the reaction chamber to restrict process gas flow in the low conductance configuration, and that moves distal a showerhead and the exhaust port to provide reduced restriction of process gas flow for reaction chamber evacuation. The chuck includes thermal control for enhancing film deposition on the substrate and for reducing residual film deposition on the chuck. An evacuation opening in the housing provides independent evacuation of residual gas from the housing.