Combined wavelength and frequency modulation spectroscopy: A novel diagnostic tool for materials processing

H. C. Sun, E. A. Whittaker, Y. W. Bae, C. K. Ng, V. Patel, W. H. Tam, S. McGuire, B. Singh, B. Gallois

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

By applying both low-frequency wavelength modulation and high-frequency phase modulation to a laser diode, we develop a sensitive, high-bandwidth chemical diagnostic tool that is applicable to a variety of gas-phase processing environments. Specific chemical species are identified and monitored through their infrared absorption spectra, and the modulation methods allow for sensitive detection that is free of window and other reflection-driven interference fringes. Absorbance limits of 5.3 × 10−8 and 1.9 × 10−7 are obtained for an AlGaAs diode laser and a lead-salt diode laser, respectively. We discuss applications to plasma etching and chemical vapor deposition.

Original languageEnglish
Pages (from-to)885-893
Number of pages9
JournalApplied Optics
Volume32
Issue number6
DOIs
StatePublished - 20 Feb 1993

Keywords

  • Laser absorption spectroscopy
  • Metal-organic chemical vapor deposition
  • Plasma etching
  • Tunable diode laser

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