Browsing by Author "Chiang, Wen-Jen"

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Dependence of Light-Accelerated Instability on Bias and Environment in Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors
(2013)
Chen, Yu-Chun
;
Chang, Ting-Chang
;
Li, Hung-Wei
;
Chung, Wan-Fang
;
Hsieh, Tien-Yu
This study examines the dependence of light-accelerated instability on bias and environment in amorphous indium-gallium-zinc-oxide thin film transistors. When device is in vacuum ambient, the threshold voltage of device after negative gate bias illumination stress (NBIS) showed bias-dependent electrical degradation behavior. However, experimental results show the degradation of electrical characteristic in a-IGZO devices does not only rely on the charge trapping mechanism for NBIS. During NBIS in oxygen, moisture-simulated and atmosphere ambient, the negative shift in electrical characteristic is suppressed when compared to that in vacuum. This implies that the adsorbent gas species in the surrounding environment dominates the electrical characteristic degradation of devices during NBIS, which leading the change of dominant mechanism from photon-created carrier trapping to adsorbed/desorbed gas phenomenon. (C) 2013 The Electrochemical Society. All rights reserved.
Investigation of gate-bias stress and hot-carrier stress-induced instability of InGaZnO thin-film transistors under different environments
(2013-09-01)
Hsieh, Tien-Yu
;
Chang, Ting-Chang
;
Chen, Te-Chih
;
Tsai, Ming-Yen
;
Chen, Yu-Te
This paper investigates the temperature and ambiance effects on various reliability issues for InGaZnO thin film transistors with an organic passivation layer. Hot-carrier stress and gate-bias stress are carried out under different environmental temperatures and ambient gases. The device exhibits relatively good stability under room temperture, whereas high temperature enhances degradation. Futhermore, different degradation behaviors after gate-bias stress in atmosphere and in vacuum can be attributed to gas adsorption/desorption-induced instability. Moreover, capacitance-voltage measurement techinique is utilized to analyze the degradation mechanism and to extract the density of state (DOS). The result reveals that the threshold voltage shift after both hot-carrier and gate-bias stress originates from the charge-trapping effect at the interface of gate insulator and active layer, with the extra trap states generated during stress responsible for C-V curve distortion. In addition, the asymmetric degradation behavior of gate-to-drain capacitance (Cgd) and gate-to-source capacitance (Cgs) indicates that trap states are generated near the drain side. (C) 2012 Elsevier B.V. All rights reserved.
Reduction of defect formation in amorphous indium-gallium-zinc-oxide thin film transistors by N2O plasma treatment
(2013-11-28)
Jhu, Jhe-Ciou
;
Chang, Ting-Chang
;
Chang, Geng-Wei
;
Tai, Ya-Hsiang
;
Tsai, Wu-Wei
An abnormal sub-threshold leakage current is observed at high temperature in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs). This phenomenon occurs due to a reduced number of defects in the device's a-IGZO active layer after the device has undergone N2O plasma treatment. Experimental verification shows that the N2O plasma treatment enhances the thin film bonding strength, thereby suppressing the formation of temperature-dependent holes, which are generated above 400 K by oxygen atoms leaving their original sites. The N2O plasma treatment devices have better stability performance than as-fabricated devices. The results suggest that the density of defects for a-IGZO TFTs with N2O plasma treatment is much lower than that in as-fabricated devices. The N2O plasma treatment repairs the defects and suppresses temperature-dependent sub-threshold leakage current. (C) 2013 AIP Publishing LLC.