Monitoring PFCs in the Electronics Industry: Instrumental Considerations
Van Gompel, Joe
Recent decisions by the US EPA concerning emissions of global warming gases could have a substantial impact on the electronics industry in the United States. Fluorocompound (FC) gases used in semiconductor manufacturing, such as CF4, C2F6, SF6, and NF3 have very high global warming potentials and are used in large quantities. The EPA reporting rule requires reporting of global warming gas emissions from facilities that exceed 15,000 tons CO2 or equivalent per year, and that level is readily attained by most fabs through the use of these FCs. Emissions can be estimated for 2009, but from 2010 on, the EPA requires verifiable testing. At the time of writing (Dec. 2009), this reporting rule has been suspended for the electronics industry pending review. Fourier transform infrared spectroscopy (FTIR) is the method of choice for analysis of FCs, as they present strong absorbances which are away from those of most other compounds, minimizing interferences. FTIR is superior for both qualitative and quantitative analysis and FCs can readily be seen in the sub-ppm concentrations when the correct equipment and instrumental parameters are used. While FTIR can readily analyze FCs, the use of an abatement device to destroy FCs raises the requirement of a tracer gas so absolute flow measurements can be performed. Argon and krypton are commonly used, but as these are invisible to infrared analysis, quadrupole mass spectrometry (QMS) is utilized. This presentation will be a brief review of FTIR and QMS, and a discussion of the correct instrumental and configurational parameters for FC emissions testing.