Numerical Analysis of Oxygen-Related Defects in Amorphous In-W-O Nanosheet Thin-Film Transistor.

Wan-Ta Fan,Chien-Min Chang,Po-Yi Kuo,Yue Kuo,Po-Tsun Liu,I-Han Liu

doi:10.3390/nano11113070

Wan-Ta Fan, Chien-Min Chang + Show 4 more

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https://doi.org/10.3390/nano11113070

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Abstract

The integration of 4 nm thick amorphous indium tungsten oxide (a-IWO) and a hafnium oxide (HfO2) high-κ gate dielectric has been demonstrated previously as one of promising amorphous oxide semiconductor (AOS) thin-film transistors (TFTs). In this study, the more positive threshold voltage shift (∆VTH) and reduced ION were observed when increasing the oxygen ratio during a-IWO deposition. Through simple material measurements and Technology Computer Aided Design (TCAD) analysis, the distinct correlation between different chemical species and the corresponding bulk and interface density of states (DOS) parameters were systematically deduced, validating the proposed physical mechanisms with a quantum model for a-IWO nanosheet TFT. The effects of oxygen flow on oxygen interstitial (Oi) defects were numerically proved for modulating bulk dopant concentration Nd and interface density of Gaussian acceptor trap NGA at the front channel, significantly dominating the transfer characteristics of a-IWO TFT. Furthermore, based on the studies of density functional theory (DFT) for the correlation between formation energy Ef of Oi defect and Fermi level (EF) position, we propose a numerical methodology for monitoring the possible concentration distribution of Oi as a function of a bias condition for AOS TFTs.

Highlights

Published: 15 November 2021Recently, n-type amorphous indium-gallium-zinc-oxide (a-IGZO) [1] has been shown to be one of the most promising materials for amorphous oxide semiconductor (AOS)-based thin-film transistors (TFTs) for achieving a low-temperature process, high-resolution, and a low-power display [2]
The measured transfer characteristics of a-IWO TFT and the extracted electrical parameters with different oxygen ratios are shown in Figure 2a and Table 1, respectively
Because the 4 nm aIWO active semiconductor was thinner than the 10 nm X-ray photoelectron spectroscopy (XPS) penetration depth, the prepared sample was 4 nm thick a-IWO film deposited on silicon substrate for analyzing chemical properties of bulk film

Summary

Introduction

N-type amorphous indium-gallium-zinc-oxide (a-IGZO) [1] has been shown to be one of the most promising materials for amorphous oxide semiconductor (AOS)-based thin-film transistors (TFTs) for achieving a low-temperature process, high-resolution, and a low-power display [2]. The AOS concept indicates that amorphous oxide is composed of heavy metal cations (HMC) with electronic configurations (n − 1)d10 ns0 (n ≥ 4) [3]. The high-mobility amorphous semiconductors can be achieved because largely spread spherical metal ns0 orbitals constitute the lowest unoccupied states (conduction band minimum, CBM), and they are expected to have a high electron mobility and a small electron effective mass in disordered amorphous structures [3]. Replacing Ga and/or Zn in InO-based semiconductors, such as InTiO, InWO. Replacing Ga and/or Zn in InO-based semiconductors, such as InTiO, InWO. etc., is an alternative way to suppress

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