AVS 47th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoA

Paper PS1-MoA8
Detection of Perfluorinated Compounds by Microplasma Optical Emission Spectroscopy

Monday, October 2, 2000, 4:20 pm, Room 310

Session: Emerging Plasma Applications
Presenter: D.D. Hsu, University of California, Berkeley
Authors: D.D. Hsu, University of California, Berkeley
D.B. Graves, University of California, Berkeley
Correspondent: Click to Email
Because of impending restrictions on the emission of perfluorinated compounds (PFCs) by the semiconductor and other industries, methods for monitoring PFC concentrations in exhaust streams will be necessary. Current methods, including Fourier transform infrared (FTIR) spectrometry and mass spectrometry, are relatively expensive and complicated. One option to detect PFCs in exhaust streams at atmospheric pressure is the use of optical emission spectroscopy (OES) from a microhollow cathode discharge (MHCD). These intense glow discharges can be stabilized at elevated pressures and therefore offer the opportunity to exploit OES under a relatively wide range of conditions. This technique presents an inexpensive and simple way to monitor PFC concentrations. The circular geometry of a microhollow cathode produces intense excitation and hence, a strong source for OES. In the results we will present, various concentrations of PFC in a diluent gas were flowed through an MHCD with a hole diameter of 200 µm, and the optical emission was analyzed. A direct current of 8 mA and a voltage of 250 V were supplied to sustain the MHCD. Concentrations as low as 10 ppm C@sub 2@F@sub 6@ in argon at 700 Torr were detected by examining atomic carbon, atomic fluorine, and molecular C@sub 2@ spectra in the visible range. A linear relationship between PFC concentration and integrated emission intensity was found. The results suggest that fluorocarbon concentrations on the order of 1 ppm can be detected with this technique. Details of the experimental setup and the observed spectra of various PFC concentrations in different diluent gases will be discussed. In addition, the results obtained suggest that MHCD OES might be a powerful analytical tool for other species as well.