Mechanistic Mapping of Ozone-Dosed Al₂O₃ Atomic Layer Deposition Half-Cycles

Despite the growing interest in the utilization of ozone (O₃) precursors as oxygen layer resources for the atomic layer deposition (ALD) of metal oxide films, relevant mechanistic studies are lacking. Herein, the density functional theory modeling approach is employed to comprehensively unveil the mechanisms of O₃-dosed Al₂O₃ ALD half-cycles based on three distinct schemes that were previously proposed for the chemical conversion of trimethylaluminum-covered surfaces into OH-covered surfaces. In scheme 1, the first step involves O₃-induced insertion of oxygen into the C–H bond of AlCH₃ surface groups. In contrast, schemes 2 and 3 both begin with oxygen insertion into the Al–C bond, although the subsequent steps differ. The computational investigation is performed from both thermodynamic and kinetic perspectives and provides meaningful insights into the relative feasibility of the three schemes. First, two key competitive steps, namely, “Al–CH₂OH versus Al–OCH₃” and “carbonate versus hydroxyl”, are verified to be decisive in determining the most thermodynamically and kinetically feasible ALD half-cycle pathway. Second, the analysis of the two key competitive steps reveals that two schemes (schemes 2 and 3) contribute competitively to the ALD half-cycle. Finally, owing to this competition, the relative feasibility of schemes 2 and 3 is strongly dependent on the process conditions. These findings are expected to be beneficial for efforts toward the careful design of O₃-dosed ALD half-cycles to produce high-purity metal oxide films.