Accurate, reliable control of process gases by mass flow controllers

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Description

The thermal mass flow controller, or MFC, has become an instrument of choice for the monitoring and controlling of process gas flow throughout the materials processing industry. These MFCs are used on CVD processes, etching tools, and furnaces and, within the semiconductor industry, are used on 70% of the processing tools. Reliability and accuracy are major concerns for the users of the MFCs. Calibration and characterization technologies for the development and implementation of mass flow devices are described. A test facility is available to industry and universities to test and develop gas floe sensors and controllers and evaluate their performance ... continued below

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11 p.

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Hardy, J. & McKnight, T. February 1, 1997.

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Description

The thermal mass flow controller, or MFC, has become an instrument of choice for the monitoring and controlling of process gas flow throughout the materials processing industry. These MFCs are used on CVD processes, etching tools, and furnaces and, within the semiconductor industry, are used on 70% of the processing tools. Reliability and accuracy are major concerns for the users of the MFCs. Calibration and characterization technologies for the development and implementation of mass flow devices are described. A test facility is available to industry and universities to test and develop gas floe sensors and controllers and evaluate their performance related to environmental effects, reliability, reproducibility, and accuracy. Additional work has been conducted in the area of accuracy. A gravimetric calibrator was invented that allows flow sensors to be calibrated in corrosive, reactive gases to an accuracy of 0.3% of reading, at least an order of magnitude better than previously possible. Although MFCs are typically specified with accuracies of 1% of full scale, MFCs may often be implemented with unwarranted confidence due to the conventional use of surrogate gas factors. Surrogate gas factors are corrections applied to process flow indications when an MFC has been calibrated on a laboratory-safe surrogate gas, but is actually used on a toxic, or corrosive process gas. Previous studies have indicated that the use of these factors may cause process flow errors of typically 10%, but possibly as great as 40% of full scale. This paper will present possible sources of error in MFC process gas flow monitoring and control, and will present an overview of corrective measures which may be implemented with MFC use to significantly reduce these sources of error.

Physical Description

11 p.

Notes

OSTI as DE97000150

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  • 126. annual meeting of the Minerals, Metals and Materials Society, Orlando, FL (United States), 9-13 Feb 1997

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  • Other: DE97000150
  • Report No.: CONF-970201--9
  • Grant Number: AC05-96OR22464
  • Office of Scientific & Technical Information Report Number: 432948
  • Archival Resource Key: ark:/67531/metadc681786

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  • February 1, 1997

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  • July 25, 2015, 2:20 a.m.

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  • Jan. 15, 2016, 12:34 p.m.

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Hardy, J. & McKnight, T. Accurate, reliable control of process gases by mass flow controllers, article, February 1, 1997; Tennessee. (digital.library.unt.edu/ark:/67531/metadc681786/: accessed September 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.