Obtaining a Low and Wide Atomic Layer Deposition Window (150–275 °C) for In₂O₃ Films Using an In^III Amidinate and H₂O

Abstract

Abstract Indium oxide is a major component of many technologically important thin films, most notably the transparent conductor indium tin oxide (ITO). Despite being pyrophoric, homoleptic indium(III) alkyls do not allow atomic layer deposition (ALD) of In 2 O 3 using water as a co‐precursor at substrate temperatures below 200 °C. Several alternative indium sources have been developed, but none allows ALD at lower temperatures except in the presence of oxidants such as O 2 or O 3 , which are not compatible with some substrates or alloying processes. We have synthesized a new indium precursor, tris( N , N′ ‐diisopropylformamidinato)indium(III), compound 1 , which allows ALD of pure, carbon‐free In 2 O 3 films using H 2 O as the only co‐reactant, on substrates in the temperature range 150–275 °C. In contrast, replacing just the H of the anionic i PrNC(H)N i Pr ligand with a methyl group (affording the known tris( N , N′ ‐diisopropylacetamidinato)indium(III), compound 2 ) results in a considerably higher and narrower ALD window in the analogous reaction with H 2 O (225–300 °C). Kinetic studies demonstrate that a higher rate of surface reactions in both parts of the ALD cycle gives rise to this difference in the ALD windows.