Non-dispersive infrared gas analyzer for vapor density measurements of a carbonyl-containing organometallic cobalt precursor

Published

December 1, 2017

Author(s)

James E. Maslar, William A. Kimes, Brent A. Sperling, Ravindra Kanjolia

Abstract

A non-dispersive infrared (NDIR) gas analyzer was demonstrated for measuring the vapor-phase density of the carbonyl-containing organometallic cobalt precursor μ2-η2-(tBu- acetylene) dicobalthexacarbonyl (CCTBA). This sensor was based on direct absorption by CCTBA vapor in the C≡O stretching spectral region and utilized a stable, broadband infrared filament source, an optical chopper to modulate the source, a bandpass filter for wavelength isolation, and a cryogenic InSb detector. The optical system was calibrated self-consistently by selecting a calibration factor to convert CCTBA absorbance to a partial pressure that, when used to calculate CCTBA flow rate and CCTBA mass removed from the ampoule, resulted in an optically-determined mass that was equal to a gravimetrically-determined mass. In situ FT-IR spectroscopy was performed simultaneously with the NDIR gas analyzer measurements in order to characterize potential interferences. Interference due to CO evolution from CCTBA was found to be small under the flow conditions employed here. A CCTBA minimum detectable molecular density as low as  3 x 1013 cm 3 was calculated with no signal averaging and for a sampling rate of 200 Hz. While this NDIR gas analyzer was specifically tested for CCTBA, it is suitable for characterizing the vapor delivery of a wide range of carbonyl-containing precursors.

Citation

Applied Spectroscopy

Volume

71

Issue

12

Pub Type

Journals

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DOI Link

Keywords

ALD, atomic layer deposition, CCTBA, CVD, chemical vapor deposition, infrared absorption, cobalt, non-dispersive infrared gas analyzer, NDIR, (tBu-acetylene) dicobalthexacarbonyl

Citation

Maslar, J. , Kimes, W. , Sperling, B. and Kanjolia, R. (2017), Non-dispersive infrared gas analyzer for vapor density measurements of a carbonyl-containing organometallic cobalt precursor, Applied Spectroscopy, [online], https://doi.org/10.1177/0003702817716939 (Accessed October 7, 2025)