Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

doi:10.1088/1674-1056/ac560f

中国物理B ›› 2022, Vol. 31 ›› Issue (9): 96101-096101.doi: 10.1088/1674-1056/ac560f

Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

Chen Wang(王琛), Wenmo Lu(路文墨), Fengnan Li(李奉南), Qiaomei Luo(罗巧梅), and Fei Ma(马飞)^†

State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China

收稿日期:2021-12-01 修回日期:2022-01-29 接受日期:2022-02-17 出版日期:2022-08-19 发布日期:2022-09-01
通讯作者: Fei Ma E-mail:mafei@mail.xjtu.edu.cn
基金资助:
Project supported by the National Natural Science Foundation of China (Grant Nos. 51771144 and 62104189), the Natural Science Foundation of Shaanxi Province, China (Grant Nos. 2021JC-06, 2019TD-020, and 2019JLM-30), the China Postdoctoral Science Foundation (Grant No. 2020M683483), and the Fundamental scientific research business expenses of Xi'an Jiaotong University (Grant No. XZY022020017).

Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

Chen Wang(王琛), Wenmo Lu(路文墨), Fengnan Li(李奉南), Qiaomei Luo(罗巧梅), and Fei Ma(马飞)^†

State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China

Received:2021-12-01 Revised:2022-01-29 Accepted:2022-02-17 Online:2022-08-19 Published:2022-09-01
Contact: Fei Ma E-mail:mafei@mail.xjtu.edu.cn
Supported by:
Project supported by the National Natural Science Foundation of China (Grant Nos. 51771144 and 62104189), the Natural Science Foundation of Shaanxi Province, China (Grant Nos. 2021JC-06, 2019TD-020, and 2019JLM-30), the China Postdoctoral Science Foundation (Grant No. 2020M683483), and the Fundamental scientific research business expenses of Xi'an Jiaotong University (Grant No. XZY022020017).

摘要/Abstract

摘要： Amorphous indium-gallium-zinc oxide (a-IGZO) thin films are prepared by pulsed laser deposition and fabricated into thin-film transistor (TFT) devices. In-situ x-ray photoelectron spectroscopy (XPS) illustrates that weakly bonded oxygen (O) atoms exist in a-IGZO thin films deposited at high O₂ pressures, but these can be eliminated by vacuum annealing. The threshold voltage (V_th) of the a-IGZO TFTs is shifted under positive gate bias, and the V_th shift is positively related to the deposition pressure. A temperature variation experiment in the range of 20 K-300 K demonstrates that an activation energy of 144 meV is required for the V_th shift, which is close to the activation energy required for the migration of weakly bonded O atoms in a-IGZO thin films. Accordingly, the V_th shift is attributed to the acceptor-like states induced by the accumulation of weakly bonded O atoms at the a-IGZO/SiO₂ interface under positive gate bias. These results provide an insight into the mechanism responsible for the V_th shift of the a-IGZO TFTs and help in the production of reliable designs.

关键词: a-IGZO thin films, weakly bonded O atoms, threshold voltage shift

Abstract: Amorphous indium-gallium-zinc oxide (a-IGZO) thin films are prepared by pulsed laser deposition and fabricated into thin-film transistor (TFT) devices. In-situ x-ray photoelectron spectroscopy (XPS) illustrates that weakly bonded oxygen (O) atoms exist in a-IGZO thin films deposited at high O₂ pressures, but these can be eliminated by vacuum annealing. The threshold voltage (V_th) of the a-IGZO TFTs is shifted under positive gate bias, and the V_th shift is positively related to the deposition pressure. A temperature variation experiment in the range of 20 K-300 K demonstrates that an activation energy of 144 meV is required for the V_th shift, which is close to the activation energy required for the migration of weakly bonded O atoms in a-IGZO thin films. Accordingly, the V_th shift is attributed to the acceptor-like states induced by the accumulation of weakly bonded O atoms at the a-IGZO/SiO₂ interface under positive gate bias. These results provide an insight into the mechanism responsible for the V_th shift of the a-IGZO TFTs and help in the production of reliable designs.

Key words: a-IGZO thin films, weakly bonded O atoms, threshold voltage shift

中图分类号: (Amorphous semiconductors, metals, and alloys)

61.43.Dq

68.35.Fx (Diffusion; interface formation) 85.30.Tv (Field effect devices)

Chen Wang(王琛), Wenmo Lu(路文墨), Fengnan Li(李奉南), Qiaomei Luo(罗巧梅), and Fei Ma(马飞)^†. Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs[J]. 中国物理B, 2022, 31(9): 96101-096101.

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Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

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