Process Gas Mass Flow Controllers

A mass flow controller (MFC) is used to control the flow of gases in a wide range of microelectronic processes. A well designed MFC maintains a constant flow within 1 percent of the full-scale flow, has a repeatabil­ity of 0.2 percent of full scale, and has a response time of 1 second to reach within 2 per­cent of the desired (command) flow; all of this is in response to any changes in command flow, upstream pressure, downstream pressure, gas temperature, or any other variations imposed on the instrument. For enhanced accuracy, simplicity, and cost-effectiveness the MFG should directly monitor gas mass (molecular) flow without the separate measurement of tem­perature and pressure.

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