Atomic layer deposition of stoichiometric In2O3 films using liquid ethylcyclopentadienyl indium and combinations of H2O and O2 plasma

Abstract

Liquid ethylcyclopentadienyl indium (InEtCp) was synthesized, and this compound exhibited superior characteristics, including a relatively high vapor pressure and thermal stability up to 250 °C. In2O3 thin films were subsequently deposited by atomic layer deposition (ALD) using the InEtCp as a precursor together with combinations of oxidants: H2O followed by O2 plasma (WpO), H2O followed by O2 (WO), O2 plasma alone (pO), and O2 plasma followed by H2O (pOW). The growth rates for In2O3 thin films using the pO and pOW processes were much smaller than those using the WO and WpO processes. A self-limiting surface reaction during the WpO process was observed with no delay in nucleation when the pulse times for InEtCp, H2O, and O2 plasma were 0.1, 2.0, and 14 s, respectively, at a growth temperature of 200 °C. For the WO and WpO processes, the In2O3 films are considered to be formed by quite different mechanisms, due to oxidation or lack thereof in the presence or absence of the -O-In-OH* intermediate product. This is due to the difference in the oxidation strength of O2 gas and O2 plasma during the oxidation step in the ALD process. As a result, In2O3 thin films deposited by WpO were obtained with a stoichiometric O/In ratio of 1.5 and a negligibly low residual carbon concentration of around TOF-SIMS detection limit, below 1 ppm. Therefore, InEtCp is one of the promising candidate precursors to form a high quality In2O3 film.

Comparison of characteristics of thin-film transistor with In2O3 and carbon-doped In2O3 channels by atomic layer deposition and post-metallization annealing in O3

“…25) In 2 O 3 -based metal oxide films have been deposited using various deposition methods, such as radio-frequency magnetron sputtering, 26) the sol-gel process, 27) solution processing, 28,29) inkjet printing, 30) CVD 31) and atomic layer deposition (ALD). [32][33][34][35][36][37][38][39][40][41][42] In 2 O 3 films deposited using sputtering at room temperature typically have a polycrystalline structure. Moreover, as-grown In 2 O 3 films deposited using sol-gel, inkjet printing and CVD methods sometimes contain residual impurities from the precursors; a hightemperature annealing process must be carried out to reduce these residual impurities.…”

Influence of adsorbed oxygen concentration on characteristics of carbon-doped indium oxide thin-film transistors under bias stress

“…Channel layers of 5 nm thick InO 1.16 C 0.04 were grown via ALD at 150 °C using an ethylcyclopentadienyl indium precursor and a sequential supply of H 2 O/O 3 oxidant gas. 41) The active channels were patterned using a combination of photolithography and dry etching processes. Ti/Au (10 nm/150 nm) films as source/ drain electrodes were subsequently formed using optical lithography, electron-beam evaporation, and lift-off processes.…”

“…24) In 2 O 3 -based metal oxide films have been deposited using various deposition methods such as radio-frequency magnetron sputtering, 25) sol-gel processing, 26) solution processing, 27,28) inkjet printing, 29) chemical vapor deposition (CVD), 30) and atomic layer deposition (ALD). [31][32][33][34][35][36][37][38][39][40][41] In 2 O 3 films deposited via sputtering at room temperature typically have a polycrystalline structure. Moreover, as-grown In 2 O 3 films deposited using solgel, inkjet printing, and CVD methods sometimes contain residual impurities from the precursors; a high-temperature annealing process must then be carried out to reduce these residual impurities.…”

Review of Material Properties of Oxide Semiconductor Thin Films Grown by Atomic Layer Deposition for Next-Generation 3D Dynamic Random-Access Memory Devices

“…This transition significantly affected the adsorption behavior of the DEZ precursor. The change in ZnO growth surface from Ga 2 O 3 to In 2 O 3 played a crucial role, as elucidated by Mizutani et al With the alkyl cyclopentadienyl In precursor and O2 plasma, the number of reactive surface sites (OH*) decreased, as each In atom required two OH* sites but replenished only one in return. In contrast, Ga 2 O 3 films offered two OH* sites.…”

“…Also, InCp precursors show fast ALD growth over wide ALD windows, such as H 2 O/O 2 (100–300 °C) or O 3 (200–450 °C). , However, it shows high resistivity such as >1.6 × 10 –2 Ω cm . Mizutani et al synthesized an ethylcyclopentadienyl indium (InEtCp) precursor that exhibits a similar structure and properties to InCp but has a relatively high vapor pressure and wide ALD window. When using InCl 3 as the precursor, excessively high deposition temperatures of approximately 500 °C are required, resulting in a low growth rate of less than 0.3 Å/cycle.…”