Atomic-Layer-Deposition of Indium Oxide Nano-films for Thin-Film Transistors

摘要

Atomic-layer-deposition (ALD) of In~(2)O~(3)nano-films has been investigated using cyclopentadienyl indium (InCp) and hydrogen peroxide (H~(2)O~(2)) as precursors. The In~(2)O~(3)films can be deposited preferentially at relatively low temperatures of 160–200?°C, exhibiting a stable growth rate of 1.4–1.5??/cycle. The surface roughness of the deposited film increases gradually with deposition temperature, which is attributed to the enhanced crystallization of the film at a higher deposition temperature. As the deposition temperature increases from 150 to 200?°C, the optical band gap (E~(g)) of the deposited film rises from 3.42 to 3.75?eV. In addition, with the increase of deposition temperature, the atomic ratio of In to O in the as-deposited film gradually shifts towards that in the stoichiometric In~(2)O~(3), and the carbon content also reduces by degrees. For 200?°C deposition temperature, the deposited film exhibits an In:O ratio of 1:1.36 and no carbon incorporation. Further, high-performance In~(2)O~(3)thin-film transistors with an Al~(2)O~(3)gate dielectric were achieved by post-annealing in air at 300?°C for appropriate time, demonstrating a field-effect mobility of 7.8?cm_(2)/V?s, a subthreshold swing of 0.32?V/dec, and an on/off current ratio of 10_(7). This was ascribed to passivation of oxygen vacancies in the device channel.