Characteristics of Ultrathin Indium Oxide Thin‐Film Transistors with Diverse Channel Lengths Fabricated by Atomic Layer Deposition

• Published in: physica status solidi (b) 2024-07, Vol.261 (7), p.n/a
• Main Authors: Lee, Ju-Hun, Kang, Seung-Youl, Yang, Jong-Heon, Pi, Jae-Eun, Hwang, Chi-Sun, Moon, Jaehyun
• Format: Article
• Language: English
• Subjects: atomic layer deposition; contact resistance; indium oxide; n-type oxide semiconductors; scaled channel length; transmission line model
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202300323

The oxide thin‐film transistors (TFTs) with ultrathin (5 nm) crystalline In2O3 channels formed by an atomic layer deposition method are fabricated. The ultrathin In2O3 films are formed at a deposition temperature of 300 °C using (3‐(dimethylamino)propyl)dimethylindium as the indium precursor and ozone as the oxidizing agent. The postannealing is performed in an oxygen atmosphere for 2 h at 300 °C. The scaling behavior of the field‐effect mobility (μFE) is investigated as a function of the channel length (Lch). As Lch increases from 5 to 160 μm, the average μFE is measured and found to increase from 20.2 to 33.6 cm2 V−1 s−1. It shows the average device properties of subthreshold swing of 0.32 V dec−1, turn‐on voltage of −5.5 V, and on/off current ratio of 107. To understand this trend, the transmission line model is utilized to extract the resistance components present across the channel quantitatively. The analyses reveal that among the components comprising the total resistance, the fraction of Rc increases as Lch becomes shorter. Thus, Rc emerges as a dominant parameter that determines μFE. In this regard, the results have technical significance in vertical TFTs and high‐resolution applications in which predictable scaling matters. To understand the impact of contact resistance (Rc) on field effect transport in ultrathin In2O3 thin‐film transistors, a transmission line model is quantitatively utilized to extract the resistance components present throughout the channel. The analyses reveal that among the components comprising the total resistance, i.e., the channel and ITO/In2O3 Rc, the fraction of Rc increases as the channel length becomes shorter.