Achieving a Low-Voltage, High-Mobility IGZO Transistor through an ALD-Derived Bilayer Channel and a Hafnia-Based Gate Dielectric Stack
- Authors
- Cho, Min Hoe; Choi, Cheol Hee; Seul, Hyeon Joo; Cho, Hyun Cheol; Jeong, Jae Kyeong
- Issue Date
- Apr-2021
- Publisher
- AMER CHEMICAL SOC
- Keywords
- atomic-layer deposition; indium-gallium zinc oxide; bilayer channel; high-kappa dielectric; high mobility; low operation voltage; bias stability; thin-film transistor
- Citation
- ACS APPLIED MATERIALS & INTERFACES, v.13, no.14, pp.16628 - 16640
- Indexed
- SCIE
SCOPUS
- Journal Title
- ACS APPLIED MATERIALS & INTERFACES
- Volume
- 13
- Number
- 14
- Start Page
- 16628
- End Page
- 16640
- URI
- https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/1283
- DOI
- 10.1021/acsami.0c22677
- ISSN
- 1944-8244
- Abstract
- Ultrahigh-resolution displays for augmented reality (AR) and virtual reality (VR) applications require a novel architecture and process. Atomic-layer deposition (ALD) enables the facile fabrication of indium-gallium zinc oxide (IGZO) thin-film transistors (TFTs) on a substrate with a nonplanar surface due to its excellent step coverage and accurate thickness control. Here, we report all-ALD-derived TFTs using IGZO and HfO2 as the channel layer and gate insulator, respectively. A bilayer IGZO channel structure consisting of a 10 nm base layer (In0.52Ga0.29Zn0.19O) with good stability and a 3 nm boost layer (In0.82Ga0.08Zn0.10O) with extremely high mobility was designed based on a cation combinatorial study of the ALD-derived IGZO system. Reducing the thickness of the HfO2 dielectric film by the ALD process offers high areal capacitance in field-effect transistors, which allows low-voltage drivability and enhanced carrier transport. The intrinsic inferior stability of the HfO2 gate insulator was effectively mitigated by the insertion of an ALD-derived 4 nm Al2O3 interfacial layer between HfO2 and the IGZO film. The optimized bilayer IGZO TFTs with HfO2-based gate insulators exhibited excellent performances with a high field-effect mobility of 74.0 +/- 0.91 cm(2)/(V s), a low subthreshold swing of 0.13 +/- 0.01 V/dec, a threshold voltage of 0.20 +/- 0.24 V, and an I-ON/OFF of similar to 3.2 x 10(8) in a low-operation-voltage (<= 2 V) range. This promising result was due to the synergic effects of a bilayer IGZO channel and HfO2-based gate insulator with a high permittivity, which were mainly attributed to the effective carrier confinement in the boost layer with high mobility, low free carrier density of the base layer with a low V-O concentration, and HfO2-induced high effective capacitance.
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