Method of and system for sub-atmospheric gas delivery with backflow control

An apparatus for monitoring and preventing backflow into a sub-atmospheric gas source, the apparatus comprising:

• a) a valve in fluid communication with the sub-atmospheric gas source, for blocking fluid communication with the gas source upon receipt of a first signal;
• b) a temperature sensor, in thermal communication with the sub-atmospheric gas source, capable of generating a second signal representative of the temperature of the sub-atmospheric gas source;
• and
• c) a valve controller unit connected to said valve and said temperature sensor, capable of generating said first signal in response to said second signal.

A system for delivering gas from a sub-atmospheric gas source to a chamber and that prevents backflow into the sub-atmospheric gas source, the system comprising:

• a) a purge stick comprising a source of purge gas, a purge line connected thereto, and further comprising in order along the purge line from said source of purge gas, a pressure switch, a first flow restrictor, a first filter and a first actuated valve;
• b) a process gas delivery stick comprising a sub-atmospheric process gas source having a blocking valve for blocking fluid communication with said sub-atmospheric gas source upon receipt of a first signal, and a process gas line fluidly connecting said valve to the chamber, said process gas delivery system further comprising in order along said process gas line from said valve to the chamber, a first pressure transducer capable of generating a second signal representative of the pressure at said first pressure transducer, said first actuated valve which fluidly connects said purge stick to said process gas delivery stick, a second actuated valve, a first isolation valve, a second pressure transducer, a third isolation valve, a second filter, a third isolation valve, a second flow restrictor, a third pressure transducer capable of generating a third signal representative of pressure at said third pressure transducer, and a fourth isolation valve;
• and
• c) an evacuation stick comprising a source of evacuation gas and an evacuation gas line connected thereto, and further comprising in order along said evacuation gas line, a fifth isolation valve, a vacuum generator having a branch evacuation line fluidly connected to said second actuated valve thereby fluidly connecting said evacuation stick to said process gas delivery stick, and a vent;
• d) a valve controller unit connected to said blocking valve, said first pressure transducer and said third pressure transducer, and capable of generating said first signal in response to said second and third signals.

A gas flow system comprising:

• a) a pipe for flowing fluid between a source and a destination;
• b) a mechanical valve in said pipe;
• c) an electronic controller for controlling the position of said valve;
• and
• d) a pressure difference sensor capable of providing a pressure difference signal to said electronic controller, wherein said controller controls the position of said valve based on said pressure difference signal, said pressure difference sensor for reading a pressure difference between two locations in the system wherein said valve is closed when the pressure is higher at a location in the system distant, than at a location near, said source.