Trace water vapor determination in corrosive gases by infrared spectroscopy
- Sandia National Labs., Albuquerque, NM (United States)
- New Mexico Univ., Albuquerque, NM (United States). Dept. of Chemistry
To extend the life of gas delivery systems and improve wafer yields, there is a need for an in-line monitor of H{sub 2}O contamination. Goal of this project is to develop such an instrument, based on infrared spectroscopy, that has a detection limit of 30 ppB or better and costs $$50K or less. This year`s work considered the application of Fourier transform infrared (FTIR) spectroscopy to H{sub 2}O detection in N{sub 2} and HCl. Using a modified commercial FTIR spectrometer and a long-path gas cell, a detection limit of about 10 ppB was demonstrated for H{sub 2}O in N{sub 2} and HCl. This includes about a factor of three improvement achieved by applying quantitative multivariate calibration methods to the problem. Absolute calibration of the instrument was established from absorptivities of prominent H{sub 2}O bands between 3600 and 3910 cm{sup {minus}1}. Methods are described to minimize background moisture in the beam path. Spectral region, detector type, resolution, cell type, and path length were optimized. Resolving the narrow H{sub 2}O bands (FWHM {approx} 0.20 cm{sup {minus}1}) is not necessary to achieve optimal sensitivity. In fact, optimal sensitivity is achieved at 2 to 4 cm{sup {minus}1} resolution, allowing the use of an inexpensive interferometer. A much smaller, second generation instrument is described that will have a conservatively estimated detection limit of 1 ppB. Since the present laboratory instrument can be duplicated in its essential parts for about $$90K, it is realistic to project a cost of $50K for the new instrument. An accessory for existing FTIR spectrometers was designed that may be marketed for as little as $10K.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 10181950
- Report Number(s):
- SAND--93-4026; ON: DE94018496; BR: GB0103012
- Country of Publication:
- United States
- Language:
- English
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