標題: Investigation of the Capacitance-Voltage Electrical Characteristics of Thin-Film Transistors Caused by Hydrogen Diffusion under Negative Bias Stress in a Moist Environment
作者: Chen, Hong-Chih
Kuo, Chuan-Wei
Chang, Ting-Chang
Lai, Wei-Chih
Chen, Po-Hsun
Chen, Guan-Fu
Huang, Shin-Ping
Chen, Jian-Jie
Zhou, Kuan-Ju
Shih, Chih-Cheng
Tsao, Yu-Ching
Huang, Hui-Chun
Sze, Simon M.
電子工程學系及電子研究所
Department of Electronics Engineering and Institute of Electronics
關鍵字: water vapor;hydrogen diffusion;amorphous indium gallium zinc oxide (a-IGZO);thin-film transistors;large displays;negative bias stress (NBS)
公開日期: 30-Oct-2019
摘要: In this study, the impact of moisture on the electrical characteristics of an amorphous In-Ga-Zn-O thin-film transistor (a-IGZO TFT) was investigated. In commercial applications of such TFTs, high stability and quality performance in humid environments are essential. During TFT operation under ambient moisture, the electrolysis of water molecules occurs via the tip electric field effect. Hydrogen diffuses from the etch-stop layer or back-channel into the main channel under a negative electric field. The hydrogen atoms act as shallow donors (which causes the carrier concentration in the channel to rise), causing the threshold voltage (V-TH) to shift in the negative direction. Hydrogen diffusion from the overlap of the source/drain and gate electrodes to the channel center caused by the tip electric field induces a significant barrier lowering and V-TH shifts in a short-channel device. However, under negative bias stress (NBS) in ambient moisture, the negative V-TH shift is more obvious in short- than in long-channel devices, indicating suppressed hydrogen diffusion in long-channel devices. This is attributed to the electrolysis of water by the tip electric field at the source, drain, and gate electrodes, which causes hydrogen to diffuse to the center of the channel. Here, a novel physical model of the capacitance-voltage (C-V) electrical property changes under ambient moisture is proposed, based on the early appearance of abnormalities in the C-V measurements. The electrolysis of water caused by the tip electric field and electrical abnormalities caused by hydrogen diffusion into the a-IGZO active layer are explained by this model. A secondary-ion mass spectrometry analysis shows that hydrogen content in the channel generally increases under NBS in ambient moisture. The degradation behavior due to moisture in a-IGZO is clarified. Thus, inhibiting the tip electric field may benefit future flexible-display and gas-sensing applications.
URI: http://dx.doi.org/10.1021/acsami.9b11637
http://hdl.handle.net/11536/153214
ISSN: 1944-8244
DOI: 10.1021/acsami.9b11637
期刊: ACS APPLIED MATERIALS & INTERFACES
Volume: 11
Issue: 43
起始頁: 40196
結束頁: 40203
Appears in Collections:Articles