Atomic layer deposition of Al2O3 using alcohol as oxygen source

초록

Aluminum oxide (Al2O3) thin films deposited by atomic layer deposition (ALD) are widely utilized in various applications, where interfacial quality and thermal stability critically influence device reliability. Conventional Al2O3 ALD processes employ trimethylaluminum (TMA) and water (H2O); however, the high reactivity and small molecular size of H2O can promote unintended surface oxidation, leading to degradation of interfacial quality. As an alternative, alcohol-based oxygen sources have been explored, yet the relationship between molecular structure of oxygen sources, surface reaction pathways, and resulting film properties remains insufficiently understood. In this work, Al2O3 ALD processes using H2O, ethanol (EtOH), and 2-methyl-3-buten-2-ol (MBO) as oxygen sources were investigated through a combination of density functional theory (DFT) calculations and experiments to elucidate the influence of molecular structure of oxygen sources on surface reaction mechanisms. DFT results reveal that the reactivity of surface-adsorbed Al-CH3 species follows the order H2O > MBO > EtOH, which qualitatively correlates with the experimentally measured growth per cycle (GPC) values for each reactant. Furthermore, the carbon contamination level follows the order EtOH > MBO > H2O, indicating that carbon-containing species are removed more effectively when using MBO compared to EtOH. These findings demonstrate how molecular structure of the reactants governs surface reactivity and film quality in Al2O3 ALD, providing mechanistic guidelines for selection of oxygen sources.

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