Abstract: A valve structure without dead-legs is provided for controlling the flow of gases in a semiconductor fabrication facility. The valve structure comprises a conduit forming a loop with three ports. Flexible metallic diaphragms are selectively operable to open and close two of the ports.

Abstract: A gas cabinet manifold is free of dead-legs both during delivery of process gas to a semiconductor fabrication tool location and during purging of the manifold. The manifold includes three similar dual valve assembly blocks. Each valve assembly block includes two valves and each of the valves has a valve chamber in which are formed three ports. Each valve also includes a mechanism for selectively closing one of its three ports. Each of the valves has one of its non-closeable ports connected via a conduit to a corresponding non-closeable port of the other valve, and the other non-closeable ports are connected by a second conduit which is connected by a third conduit to a port by which gas may be introduced into the valve block. A vacuum venturi or other vacuum source is used to vent process gas from a high pressure area of the manifold by way of a pressure regulator and a low pressure area of the manifold.