Patent ID: 6581623
Filing Date: 2003-06-24
Classification: B01D,F17C,G05D,Y10T

Abstract:
An auto-switching sub-atmospheric pressure gas delivery system, comprising:a gas dispensing manifold; a plurality of sub-atmospheric pressure gas supply vessels, each said gas supply vessel being joined to the gas dispensing manifold and including a vessel valve that is selectively openable to establish gas flow communication of the gas supply vessel with the gas dispensing manifold, and selectively closeable to terminate gas flow communication of the gas supply vessel with the gas dispensing manifold; a plurality of flow control valves in the gas dispensing manifold positioned in the manifold downstream from the vessel valve of the associated sub-atmospheric pressure gas supply vessel, each control valve associated with a corresponding upstream and downstream pressure transducer and one of the plurality of sub-atmospheric pressure gas supply vessels; at least one mass flow controller downstream of said gas manifold and upstream of a process tool to provide a steady-state, uninterrupted flow of gas from the gas supply vessel to the process tool; a plurality of bleed flow passages, each associated with a corresponding one of the flow control valves in the gas dispensing manifold and arranged to flow gas therethrough in bypassing relationship to the associated flow control valve, at a restricted low flow rate in relation to flow rate of gas through the associated flow control valve when the associated flow control valve is open and gas is flowed therethrough from an associated sub-atmospheric pressure gas supply vessel, wherein a flow conductance of said bleed flow passages ensures a gradual pressure increase downstream of said flow control valves; and a CPU operatively linked to the valves and pressure transducers, for switching of the gas supply vessels for flow of gas from a selected one of the plurality of gas supply vessels to the manifold until its depletion followed by switching to a new selected one of the plurality of gas supply vessels to the manifold by selectively operating the vessel valves and flow control valves so that dispensing pressure is maintained in the manifold appropriate to prevent destabilizing perturbations of the mass flow controllers from occurring.