Effect of Various Oxidants on Reaction Mechanisms, Self-Limiting Natures and Structural Characteristics of Al2O3 Films Grown by Atomic Layer Deposition

The present study investigates the Al2O3 films grown by low-temperature atomic layer deposition (ALD) with water vapor (H2O), oxygen plasma (O-2 plasma), and ozone gas (O-3) serving as oxidants. The reaction processes with different oxidants are examined by in situ quadrupole mass spectrometry analysis of the gas phase species, which reveals a possible sequential reaction mechanism of trimethylaluminum and O-2 plasma. The coefficient of standard deviation (CSD) of the oscillation frequency change of the in situ quartz crystal microbalance (f) to represent the self-limiting nature of the films is used, and an obvious relationship is observed between the CSD of f values and the density of ALD films, which suggests the intrinsic relationship between the structural characteristics and the self-limiting natures of the ALD processes outside the temperature window. Fourier transform infrared spectroscopy reveals a large number of OCO, CO, and CH bonds remaining in the H2O-based Al2O3 films, and the smallest concentration of carbon species is found to remain in the O-3-based Al2O3 films, which explains the sources of the different self-limiting natures and structural characteristics for the different oxidant-based Al2O3 films.