Method and apparatus for controlling gas flow to a processing chamber

Apparatus for delivering gases to a semiconductor processing chamber, comprising:

• a plurality of gas inlet ports each connecting to a gas source;
• a plurality of gas outlet ports selectively in fluid communication with the plurality of gas inlet ports and first and second gas inlets of the processing chamber;
• at least two flow ratio controllers each coupling to one of the plurality of gas outlet ports, the flow ratio controller splitting the flow exiting each gas outlet port;
• and
• a flow restrictor coupled to one of the plurality of gas outlet ports, wherein the flow restrictor is sized to provide flow conditions that are substantially equal to flow conditions of the first and second gas inlets of the processing chamber.

Apparatus for delivering gases to a semiconductor processing chamber, comprising:

• a main gas delivery having at least one gas inlet port and at least one gas outlet port, wherein the at least one gas inlet port couples to a gas source and the least one gas outlet port is in fluid communication with the at least one gas inlet and the processing chamber;
• two flow ratio controllers configured to split the gas flow exiting the least one gas outlet port;
• an upstream pressure sensor disposed between the at least one gas outlet port and the two flow ratio controllers for measuring a pressure upstream of the two flow ratio controllers;
• and
• a downstream pressure sensor disposed between the two flow ratio controllers and the processing chamber for measuring a pressure downstream of the two flow ratio controllers,
• wherein the two flow ratio controllers are controlled such that a pressure differential between upstream and downstream of the two flow ratio controllers is sufficient to maintain supersonic flow through the two flow ratio controllers.