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Using diode laser spectroscopy to monitor process gas purity.

Diodenlaser-Spektroskopie für die Überwachung der Reinheit von Prozeßgasen
: Dornisch, D.; Grisar, R.; Kästle, R.; Scholz, C.; Tacke, M.

Microcontamination (1991), pp.27-31 : Abb.,Lit.
Journal Article
Fraunhofer IPM ()
Laser Gas Analysis; Lasermeßtechnik; Niederfeuchte; process control; process gas; Prozeßgas; Prozeßkontrolle; Spurengas; trace gas; Water Traces

Continuing advances in semiconductor and other ultraclean manufacturing technologies have increased the importance of all types of contamination control programs and created a need for measurement techniques with greater sensitivities than those in common use. High-resolution spectroscopy using a diode laser light source is a promising method under consideration for monitoring process gas purity. It already has proven very effective in environmental research, where trace pollutants in the atmosphere have to be detected down to the parts-per-trillion range. The technique not only combines high sensitivity with high selectivity, it has good measurement speed: Millisecond resolutions at a parts-per-million sensitivity have been demonstrated, and resolutions at a parts-per-billion sensitivity have been achieved in minutes. The study reported on this article demonstrates the applicability of diode laser spectroscopy in detecting trace contaminants in ultrapure process gases. The "worst-case scenario" of moisture vapor (H2O) in ammonia (NH3) was chosen as the test system.