Obtaining a Low and Wide Atomic Layer Deposition Window (150–275 °C) for In2O3 Films Using an InIII Amidinate and H2O. Issue 38 (5th June 2018)

• Record Type: Journal Article
• Authors: Kim, Sang Bok; Jayaraman, Ashwin; Chua, Danny; Davis, Luke M.; Zheng, Shao‐Liang; Zhao, Xizhu; Lee, Sunghwan; Gordon, Roy G.
• Is Part Of: Chemistry. Volume 24:Issue 38(2018)
• Page Start: 9525
• Page End: 9529
• Publication Date: 2018-06-05
• Subjects: amidinate -- atomic layer deposition -- indium -- thin films -- transparent conducting oxide; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201802317
• Languages: English
• ISSNs: 0947-6539

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 In2 O3 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 O2 or O3, 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 In2 O3 films using H2 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 H2 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. Abstract : Synthesis of tris( N, N′ ‐diisopropylformamidinato)indium(III) (1 )enables atomic layer deposition (ALD) of In2 O3 films suitable as transparent conducting oxides at 150 °C, the lowest temperature of processes using In III precursors and only H2 O as an oxygen source. It was observed that the ALD reactions of H2 O are completed faster when the initial surface is saturated with chemisorbed1 than with chemisorbed tris( N, N′ ‐diisopropylacetamidinato)indium(III).