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In-Situ Metrology to Characterize Water Vapor Delivery during Atomic Layer Deposition



Tariq Ahmido, William A. Kimes, Brent A. Sperling, Joseph T. Hodges, James E. Maslar


Water is often employed as the oxygen source in metal oxide atomic layer deposition (ALD) processes. It has been reported that variations in the amount of water delivered during metal oxide ALD can impact the oxide film properties. Hence, one contribution to optimizing metal oxide ALD processes would be to identify methods to better control water dose. The development of rapid, quantitative techniques for in situ water vapor measurements during ALD processes would be beneficial to achieve this goal. In this report, the performance of an in situ tunable diode laser absorption spectroscopy (TDLAS) scheme for performing quantitative, time-dependent water partial pressure measurements in a representative quarter-inch ALD delivery line is described. This implementation of TDLAS utilizes a near-IR distributed-feedback diode laser and wavelength modulation spectroscopy and provides measurement of water partial pressure on a timescale comparable to or shorter than the timescale of the gas dynamics in typical ALD systems. Depending on the degree of signal averaging, this TDLAS system was capable of measuring the water partial pressure with a detection limit in the range of ≈ 0.80 Pa to ≈ 0.08 Pa. The utility of this TDLAS scheme was demonstrated on a representative water delivery system by identifying performance characteristics that would be difficult to identify a priori without such a measurement technique.
Journal of Vacuum Science and Technology A


ALD, atomic layer deposition, tunable diode laser absorption spectroscopy, TDLAS, water vapor, water delivery


Ahmido, T. , Kimes, W. , Sperling, B. , Hodges, J. and Maslar, J. (2016), In-Situ Metrology to Characterize Water Vapor Delivery during Atomic Layer Deposition, Journal of Vacuum Science and Technology A, [online], (Accessed April 20, 2024)
Created May 2, 2016, Updated March 23, 2017