Near-Ideal Top-Gate Controllability of InGaZnO Thin-Film Transistors by Suppressing Interface Defects with an Ultrathin Atomic Layer Deposited Gate Insulator

Jiye Li; Yuqing Zhang; Jialiang Wang; Huan Yang; Xiaoliang Zhou; Mansun Chan; Xinwei Wang; Lei Lu; Shengdong Zhang

doi:10.1021/acsami.2c20176

Near-Ideal Top-Gate Controllability of InGaZnO Thin-Film Transistors by Suppressing Interface Defects with an Ultrathin Atomic Layer Deposited Gate Insulator

ACS Appl Mater Interfaces. 2023 Feb 15;15(6):8666-8675. doi: 10.1021/acsami.2c20176. Epub 2023 Jan 29.

Authors

Jiye Li¹, Yuqing Zhang², Jialiang Wang³, Huan Yang¹, Xiaoliang Zhou¹, Mansun Chan², Xinwei Wang³, Lei Lu¹, Shengdong Zhang^{1

4}

Affiliations

¹ School of Electronic and Computer Engineering, Peking University, Shenzhen 518055, China.
² Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong 999077, China.
³ School of Advanced Materials, Peking University, Shenzhen 518055, China.
⁴ School of Integrated Circuits, Peking University, Beijing 100871, China.

PMID: 36709447
DOI: 10.1021/acsami.2c20176

Abstract

An ultrathin atomic-layer-deposited (ALD) AlO_x gate insulator (GI) was implemented for self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). Although the 4.0-nm thick AlO_x exhibited ideal insulating properties, the interaction between ALD AlO_x and predeposited a-IGZO caused a relatively defective interface, thus giving rise to hysteresis and bias stress instabilities. As analyzed using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and the Hall measurement, the chemical reaction between the ALD precursor and a-IGZO is revealed. This was effectively prevented by preoxidizing a-IGZO with nitrous oxide (N₂O) plasma. With 4 nm-AlO_x GI and low-defect interfaces, high performance and stability were simultaneously achieved on SATG a-IGZO TFTs, including a near-ideal record-low subthreshold swing of 60.8 mV/dec, a low operation voltage below 0.4 V, a moderate mobility of 13.3 cm²/V·s, a low off-current below 10^-13 A, a large on/off ratio over 10⁹, and negligible threshold-voltage shifts less than 0.04 V against various bias-temperature stresses. This work clarifies the vital interfacial reaction between top-gate high-k dielectrics and amorphous oxide semiconductors (AOSs) and further provides a feasible way to remove this obstacle to downscaling SATG AOS TFTs.

Keywords: N2O treatment; a-IGZO; atomic layer deposition (ALD); bias stability; interfacial reaction; low operation voltage; self-aligned top-gate (SATG); ultrathin AlOx.