H2O-based atomic layer deposition mechanism of aluminum oxide using trimethylaluminum

As a nanofabrication technology, atomic layer deposition (ALD) has been widely used in the fields of displays, microelectronics, nanotechnology, catalysis, energy and coatings. It demonstrates excellent conformality, large-area uniformity and precise control of the sub-monolayer film. Al₂O₃ ALD using trimethylaluminum (TMA) and water (H₂O) as precursors is the most ideal ALD model system. In this work, the reactions of TMA and H₂O with the surface have been investigated using density functional theory (DFT) calculations in order to obtain more information on the reaction mechanism of the complicated H₂O-based ALD of Al₂O₃. In the TMA reaction, the methyl ligands can be eliminated and new Al-O bonds can be formed via ligand exchange reactions. In the H₂O reaction, the methyl ligand on the surface can be further eliminated and new AlO bonds can be formed. Meanwhile, the coupling reactions between the surface methyl and hydroxyl groups can further form new AlO bonds and release CH₄ or H₂O to densify the Al₂O₃ film. These complicated reaction mechanisms of Al₂O₃ H₂O-based ALD can provide theoretical guidance for the precursor design and ALD growth of other oxides and aluminum-based compounds.