Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Detection of trace water vapor in high purity phosphine using cavity ring-down spectroscopy



H. H. Funke, Mark W. Raynor, Kristine A. Bertness, Yu-Hsuan Chen


The presence of trace water vapor in process gases such as phosphine, used for compound semiconductor epitaxial growth, can negatively affect the optical and electrical properties of the final device. Therefore, sensitive water measurement techniques are required to monitor precursor purity and detect unacceptable contamination levels. A commercial cavity ring-down spectrometer that monitors a water absorption line at a wavelength of 1392.53 nm was investigated for service in high purity PH3. Spectral parameters such as the line shape of water vapor in the presence of PH3 as well as background features due to PH3 were measured at different pressures and incorporated into the data analysis software for accurate moisture readings. Test concentrations generated with a diffusion vial-based water source and dilution manifold were used to verify instrument accuracy, sensitivity, linearity, and response time. Water readings at 13.2 kPa corresponded well to added concentrations (slope=0.990 +or-} 0.01) and were linear in the tested range (0-52.7 nmol mol-1). The analyzer was sensitive to changes in water concentration of 1.3 nmol mol-1 based on 3ς of the calibration curve intercept for a weighted linear fit. Local PH3 absorption features that could not be distinguished from the water line were present in the purified PH3 spectra and resulted in an additional systematic uncertainty of 9.0 nmol mol-1. Equilibration to changing water levels at a flow rate of 80 std cm3 mins-1 PH3 occurred in 10-30 minutes. The results indicate that cavity ring-down spectroscopy (CRDS) at 1392.53 nm may be useful for applications such as on-line monitoring (and dry-down) of phosphine gas delivery lines or the quality control of cylinder sources.
Applied Spectroscopy


cavity ring-down spectroscopy, Gas purification, hydride gases, impurities


Funke, H. , Raynor, M. , Bertness, K. and Chen, Y. (2007), Detection of trace water vapor in high purity phosphine using cavity ring-down spectroscopy, Applied Spectroscopy, [online], (Accessed July 24, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 17, 2007, Updated October 12, 2021