Reducing particulates during semiconductor fabrication

A system for pumping down pressurized gas residing after shut-off in the piping use to provide a gas flow to facilitate backside wafer heating/cooling during the processing of a semiconductor wafer and including a valve selectable secondary piping line for equalizing on shutoff any pressure differential occurring in the primary gas flow line between the process chamber and the backside heating element. The secondary line runs from an opening in the process chamber wall to a tee-joint installed in the primary flow line immediately downstream of the final isolation valve in the primary line. A valve is installed in the secondary line and is operationally interlocked, in an inverse manner, with the isolation valve in the primary line such that when one valve is open the other valve is closed and vice versa.