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Quantum Cascade Laser-Based Measurement of Metal Alkylamide Density During Atomic Layer Deposition



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


An in situ gas-phase diagnostic for the metal alkylamide compound tetrakis(ethylmethylamino) hafnium (TEMAH), Hf[N(C2H5)(CH3)]4, was demonstrated. This diagnostic is based on direct absorption measurement of TEMAH vapor using an external cavity quantum cascade laser operating at 979 cm 1, the most intense TEMAH absorption in the mid-infrared spectral region, and employing 50 kHz amplitude modulation with synchronous detection. Measurements were performed in a single-pass configuration (10 cm pathlength) in a research-grade atomic layer deposition (ALD) chamber. To examine the sensitivity of this technique for use as a TEMAH delivery monitor, this technique was demonstrated in the absence of any other deposition reactants or products, and to examine the selectivity of this technique in the presence of deposition products that potentially interfere with detection of TEMAH vapor, it was demonstrated during ALD of hafnium oxide using TEMAH and water. This technique successfully detected TEMAH at molecular densities present during simulated industrial ALD conditions. During hafnium oxide ALD using TEMAH and water, absorbance from gas-phase reaction products did not interfere with TEMAH measurements while absorption by reaction products deposited on the optical windows did interfere, although interfering absorption by deposited reaction products corresponded to only 3 % of the total derived TEMAH density. With short measurement times and appropriate signal averaging, estimated TEMAH minimum detectable concentrations as low as 6 x 10 6 mol/m3 (4 x 1012 molecules/cm3) could be obtained. While this technique was demonstrated specifically for TEMAH delivery and hafnium oxide ALD using TEMAH and water, it should be readily applicable to other metal alkylamide compounds and associated metal oxide and nitride deposition chemistries, assuming similar metal alkylamide molar absorption coefficients and molecular densities in the measurement chamber.
Applied Spectroscopy


ALD, atomic layer deposition, infrared absorption, laser spectroscopy, metal alkylamide, quantum cascade laser, TEMAH, tetrakis(ethylmethylamino) hafnium


Maslar, J. , Kimes, W. and Sperling, B. (2012), Quantum Cascade Laser-Based Measurement of Metal Alkylamide Density During Atomic Layer Deposition, Applied Spectroscopy, [online], (Accessed April 17, 2024)
Created March 1, 2012, Updated November 10, 2018