Mechanistic Investigation on Thermal Atomic Layer Deposition of Group 13 Oxides

Atomic layer deposition (ALD), based on self-limiting surface reactions, has been proven as a superior deposition method for synthesis of nanoscale thin films. In the field of oxide ALD, alumina (Al2O3) is the most widely and thoroughly studied, prominently through using trimethylaluminum (TMA) with water (H2O). However, there is less information about other group 13 element (B, Ga, and In) oxides using analogous trimethyl precursors. In this study, we investigate these precursors' detailed adsorption and oxidation mechanisms during thermal ALD using density functional theory (DFT). The hydroxyl-terminated surface is transformed to a methyl-terminated surface after reacting with the trimethyl precursors. For such reaction, the reactivity of trimethylboron is significantly lower than other precursors. Meanwhile, using H2O, oxidation of the surface methyl is facile only for -Al-CH3, and stronger oxidants such as H2O2 or O-3 are required for the oxidation reactions during ALD of B, Ga, and In oxides.