Browsing by Author "Chou, Yi-Teh"

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Ambient Stability Enhancement of Thin-Film Transistor With InGaZnO Capped With InGaZnO:N Bilayer Stack Channel Layers
(2011-10-01)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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Li, Fu-Hai
;
Fuh, Chur-Shyang
A thin-film transistor (TFT) with bilayer stack structure of amorphous nitrogenated InGaZnO (IGZO) (a-IGZO:N) on an IGZO channel is proposed to enhance device stability. The a-IGZO: N acting as a back-channel passivation (BCP) is formed sequentially just after the sputter-deposited amorphous IGZO (a-IGZO) film with in situ nitrogen incorporation process. The a-IGZO:N can effectively prevent the a-IGZO channel from exposing to the atmosphere and retarding interactions with ambient oxygen species. Also, the optical energy bandgap of the a-IGZO:N film is decreased due to the addition of nitrogen. This causes the a-IGZO TFT with a-IGZO:N BCP to exhibit high immunity to the ultraviolet-radiation impact.
Characteristics imrovement for flexible a-Si:H Thin Film Transistor with post treatment processes
(2010)
Teng, Li-Feng
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Liu, Po-Tsun
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Chou, Yi-Teh
;
Fan, Yang-Shun
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光電工程學系
The performances of flexible a-Si:H TFTs on stainless foil with and without silicon nitride passivation layer were discussed in this study. The experiment results indicated the reliability of a-Si:H TFTs with passivation layer under mechanical strains was improved. That\'s related to the hydrogen passivating effect during deposition and post-annealing process.
Charge pumping method for photosensor application by using amorphous indium-zinc oxide thin film transistors
(2009-06-15)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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光電工程學系
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顯示科技研究所
The study investigated the photoreaction behavior of amorphous indium-zinc oxide thin film transistor (a-IZO TFT), which was thought to be insensitive to visible light. The obvious threshold voltage shift was observed after light illumination, and it exhibited slow recovery while returning to initial status. The photoreaction mechanism is well explained by the dynamic equilibrium of charge exchange reaction between O(2(g)) and O(2) in a-IZO layer. A charge pumping technique is used to confirm the mechanism and accelerate recoverability. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFT is also demonstrated in this work.
Electrical performance and photo-responses enhancement by in situ nitrogen incorporation to amorphous InGaZnO thin-film transistors
(2011)
Teng, Li-Feng
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Liu, Po-Tsun
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Fuh, Chur-Shyang
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Chou, Yi-Teh
;
Li, Fu-Hai
We studied wavelength dependent photo-responses in amorphous nitrogenated InGaZnO thin-film transistors (a-IGZO:N TFTs). The a-IGZO:N active layer was deposited by dc reactive sputter with a nitrogen and argon gas mixture at room temperature and performed the superior characteristics while comparing with the intrinsic IGZO TFTs.
Environment-dependent metastability of passivation-free indium zinc oxide thin film transistor after gate bias stress
(2009-12-07)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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光電工程學系
;
顯示科技研究所
We investigated the effects of bias stress on a passivation-free InZnO thin-film transistors (a-IZO TFTs) exposed to either the atmosphere or a vacuum. The magnitude of threshold voltage shift increased with the application duration of bias stress, to an extent that was much larger in the atmosphere than in the vacuum. The threshold voltage recovered slowly to its nearly initial value when the gate bias stress was removed. The electrical metastability was attributed to the interaction between the exposed a-IZO backchannel and oxygen/moisture from the atmosphere, and a dynamic equilibrium was finally achieved, regardless of the polarity of stress voltage. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3272016]
High-gain complementary inverter with InGaZnO/pentacene hybrid ambipolar thin film transistors
(2010-08-23)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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Fuh, Chur-Shyang
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光電工程學系
Ambipolar thin film transistors (TFTs) with InGaZnO/pentacene heterostructure channels are demonstrated for a high-voltage-gain complementary metal oxide semiconductor (CMOS) inverter. The ambipolar TFT exhibits a electron mobility of 23.8 cm(2)/V s and hole mobility of 0.15 cm(2)/V s for the InGaZnO and pentacene, respectively. The thermal annealing process was also studied to adjust electron concentration reducing operating voltage of the CMOS inverter. The voltage gain achieves as high as 60 obtained in the first and third quadrants of the voltage transfer characteristic. The high performance and simple manufacture of the heterostructure CMOS inverter show promise as critical components in various electrical applications. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483616]
Improvement of Electron-Gun Evaporated Aluminum Oxide for Pentacene Thin-Film Transistor
(2009)
Liu, Po-Tsun
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Chou, Yi-Teh
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Kao, Yi-Yu
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光電工程學系
;
顯示科技研究所
Supercritical fluid (SCF) technology was proposed to improve the dielectric properties of electron-gun evaporated aluminum oxide (AlO(x)) film in this work. The leakage current of AlO(x) film deposited at room temperature was suppressed significantly from 10(-4) to 10(-10) A at a bias voltage of -20 V after the SCF treatment mixed with water and propyl alcohol. The evolution of the leakage conduction mechanism was confirmed theoretically from trap-assisted quantum tunneling to the Schottky emission process due to the reduction of electric traps in the AlO(x) dielectric film. In addition, our work demonstrated the application of SCF-treated AlO(x) gate dielectric to a pentacene-based thin-film transistor.
Investigation on thin-film-transistors with a transparent material Zinc-Oxide layer with DC sputter deposition system
(2007)
Chou, Yi-Teh
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Huang, Chen-Shuo
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Shiau, S. J.
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Liu, Po-Tsun
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Chu, Li-wei
We have successfully developed a transparent thin film transistor (TTFT) with a novel material Zinc Oxide (ZnO) as semiconductor layer. The use of ZnO-based material can increases the field-effect mobility of TFT devices, the opening of AMLCD panel and releases the issue of photo-excited leakage current. In this work, the ZnO film was deposited in DC glow discharge plasma sputter system which is suitable for industrial technique and novel method in ZnO-base TFT process. With changing mixture gas flow, we can adjust the rate of Zn/ZnO mixture, Zn1+xO, and ZnO and get a suitable condition for TFT device. FTIR, XRD, SEM and AFM were utilized to analyze the characteristic of ZnO films.
Nitrogenated amorphous InGaZnO thin film transistor
(2011-01-31)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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Li, Fu-Hai
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Shieh, Han-Ping
This work presents the electrical characteristics of the nitrogenated amorphous InGaZnO thin film transistor (a-IGZO:N TFT). The a-IGZO: N film acting as a channel layer of a thin film transistor (TFT) device was prepared by dc reactive sputter with a nitrogen and argon gas mixture at room temperature. Experimental results show that the in situ nitrogen incorporation to IGZO film can properly adjust the threshold voltage and enhance the ambient stability of a TFT device. Furthermore, the a-IGZO: N TFT has a 44% increase in the carrier mobility and electrical reliability and uniformity also progress obviously while comparing with those not implementing a nitrogen doping process. (C) 2011 American Institute of Physics. [doi:10.1063/1.3551537]
Photosensor application of amorphous InZnO-based thin film transistor
(2010)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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光電工程學系
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Department of Photonics
Thin film transistor (TFT) device structure with transparent conductive oxide semiconductor is proposed for the photosensor application. The adoption of TFT-based photosensor device also is promising to be integrated with pixel-array circuits in a flat panel display and realize the system-on-panel (SoP) concept. The photosensitive TFT device can be applied to sense the ambient light brightness and then give the feedback to the backlight system adjusting the backlight intensity for the power-saving green displays. In this work, we studied the photosensitivity of amorphous indium zinc oxide (a-IZO) TFT to ultraviolet light. The a-IZO-based semiconductors have been paid much attention due to their uniform amorphous phase and high field-effect carrier mobility characteristics. The obvious threshold voltage shift was observed after light illumination, and exhibited slow recovery while returning to initial status after removing the light source. This mechanism for the photoreaction is well explained by the dynamic equilibrium of charge exchange reaction between O(2(g)) and O(2)(-) in the backchannel region of IZO-based films. An electrical trigger using charge pumping method is used to confirm the proposed mechanism and accelerate photoreaction recoverability for the first time. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFTs is also demonstrated in this paper.
Retarded Photoreaction Reversibility of a-IZO TFT for Light Sensor Applications
(2009)
Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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Chu, Chun Hung
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Shieh, Han-Ping D.
The retarded photoreaction reversibility of a-IZO TFT has been discussed in this work. With a small DC voltage bias, the reaction was speeded up and the electrical characteristics were recovered back to the fresh state. The V(th) shifting behavior possesses the potential for the light sensor applications in display technologies.
Role of environmental and annealing conditions on the passivation-free in-Ga-Zn-O TFT
(2011-12-30)
Fuh, Chur-Shyang
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Sze, Simon Min
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Liu, Po-Tsun
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Teng, Li-Feng
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Chou, Yi-Teh
We examined the characteristics of passivation-free amorphous In-Ga-Zn-O thin film transistor (a-IGZO TFT) devices under different thermal annealing atmospheres. With annealing at higher temperature, the device performed better at the above-threshold operation region, which indicated the film quality was improved with the decrease of defects in the a-IGZO active region. The mobility, threshold voltage and subthreshold swing of a-IGZO TFT annealed at 450 degrees C was 7.53 cm(2)/V s, 0.71 V and 0.18 V/decade, respectively. It was also observed that the a-IGZO was conductive after thermal annealing in the vacuum, due to the ease of oxygen out-diffusion from the a-IGZO back channel. The oxygen deficiency resultantly appeared, and provided leaky paths causing electrical unreliability when TFT was turned off. In contrast, the annealing atmosphere full of O(2) or N(2) would suppress the oxygen diffusion out of the a-IGZO back channel. The worst Vth degradation of a-IGZO TFT after positive gate bias stress and negative gate bias stress (NGBS) was about 2 V and -2 V, respectively. However, the V(th) shift in the NGBS testing could be suppressed to -0.5 V in vacuum chamber. Material analysis methods including X-ray photoelectron spectroscopy and scanning electron microscopy were used to investigate the change of a-IGZO film after different thermal annealing treatments. The variation of O 1s spectra with different annealing atmospheres showed the consistence with our proposed models. (C) 2011 Elsevier B.V. All rights reserved.
Role of Oxygen in Amorphous In-Ga-Zn-O Thin Film Transistor for Ambient Stability
(2013)
Fuh, Chur-Shyang
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Liu, Po-Tsun
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Chou, Yi-Teh
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Teng, Li-Feng
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Sze, S. M.
The role of oxygen in amorphous InGaZnO thin film transistor (a-IGZO TFT) is studied for the device ambient stability. The threshold voltage (Vth) value of 350 degrees C annealed a-IGZO TFT decreased apparently with the staying duration, and the average value shifted from 10.2 V to 5.8 V after a 9-day staying at the atmosphere. After raising the annealing temperature to 450 degrees C, the electrical stability issue was improved significantly with superior electrical parameters, including low threshold voltage (V-th), low subthreshold swing, high carrier mobility and a small V-th variation of +/- 0.5 V. It can be attributed to the enhancement of bonding energy of oxygen in the thermally-annealed a-IGZO film with the increase of thermal annealing temperatures. Besides, the stronger oxygen bonding could also suppress the absorption/desorption and UV-induced migration at the back surface, causing better electrical reliability and immunity against UV radiation, respectively. All these results showed the ambient stability is greatly related to the oxygen in a-IGZO film, and the desired electrical characteristic can be achieved via the optimization of thermal annealing process. (C) 2012 The Electrochemical Society. All rights reserved.
Spin-on ZnO thin film transistors with oxidation treatment
(2007)
Huang, Chen-Shuo
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Chou, Yi-Teh
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Liu, Po-Tsun
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Chung, Wan-Fang
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Huang, Chien-Jui
The ZnO TFTs was fabricated by spin-on method and investigated by modulating deposition environments. It was discovered that the conductivity of ZnO TFTs can be obviously changed by modulating curing temperature and the performances can be improved by incorporating oxygen.
The polarity bias control of Indium Zinc Oxide Thin Film Transistor for gas sensor application
(2010)
Teng, Li-fang
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Liu, Po-Tsun
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Chou, Yi-Teh
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Fan, Yang-Shun
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光電工程學系
An obvious Vth shift was observed after gate-bias stress and recovered. This metastability was attributed to the interaction between the exposed a-IZO backchannel and oxygen/moisture from the atmosphere, regardless of the polarity of stress voltage. This water/moisture sensitivity characteristic can be used for gas sensor application.
Thin Film Transistor with Al-Ni-La Alloy Gate Metallization Technology
(2011)
Liu, Po-Tsun
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Chou, Yi-Teh
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Hsu, Ting-Hao
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Fuh, Chur-Shyang
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平面顯示技術碩士學位學程
In this study, an aluminum-nickel-lanthanum (Al-Ni-La) alloy is introduced, for the first time, to hydrogenated amorphous silicon thin film transistor (a-Si: H TFT) for gate metallization technology. Ni atoms in Al-Ni-La can effectively improve contact characteristic with ITO film, while La can increase the uniformity of contact resistance during film deposition compared to the conventional Al-Nd alloy. Besides, Al-Ni-La alloy has advantages of a simple process and better prevention against hillock issues, which benefits active matrix liquid-crystal display (AMLCD) manufacture. The Al-Ni-La gate thin film transistor (TFT) also exhibited reliable electrical characteristics. The process compatibility with typical TFT manufacture makes Al-Ni-La gate metallization greatly promising for AMLCD technology application. (c) 2010 The Electrochemical Society. [DOI: 10.1149/1.3516178] All rights reserved.
Transportation model establishment of InGaZnO for thin film transistor device application
(2010)
Teng, Li-Feng
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Liu, Po-Tsun
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Chou, Yi-Teh
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Fan, Yang-Shun
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光電工程學系
The transportation model of on electrical metastability of a-InGaZnO TFT is established. The generation of oxygen vacancies by the annealing in a vacuum led to an increased loll and large Vth shifts, while N-2 and O-2 ambience effectively improve the device performance. A physical mechanism is also reasonably proposed.
Using electroless plating Cu technology for TFT-LCD application
(2010-11-25)
Liu, Po-Tsun
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Chou, Yi-Teh
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Su, Chih-Yu
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Chen, Hung-Ming
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光電工程學系
This study investigates the feasibility of using electroless plating (ELP) technology to manufacture copper (Cu) gate electrodes in thin film transistors (TFTs). The problem of poor adhesion between Cu and glass substrates is overcome by introducing ELP nickel-phosphorus (NiP) layers. Copper pattern formation with a desired taper can be self-aligned subsequently on a NiP layer without any layer etching process. ELP Cu film shows an obvious (111) preferred orientation, which may enhance the electrode's anti-electromigration ability. The electrical characteristics of the ELP Cu gate TFT are also similar to those of the sputter-deposited Cu gate TFT. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.