Browsing by Author "Lu, Hsueh-Hsing"

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Abnormal Dual Channel Formation Induced by Hydrogen Diffusion From SiNx Interlayer Dielectric in Top Gate a-InGaZnO Transistors
(2017-03-01)
Chen, Guan-Fu
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Chang, Ting-Chang
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Chen, Hua-Mao
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Chen, Bo-Wei
;
Chen, Hong-Chih
This letter investigates effects of different channel dimensions in top-gate a-InGaZnO4 thin-film transistors with SiNx interlayer dielectric. In narrow channel devices, hydrogen atoms in the SiNx layer diffuse into the entire active layer, inducing a single channel. However, in wider channel devices, the diffusion distance for hydrogen atoms is insufficient to affect the whole channel, instead inducing a double channel. In addition, under hot carrier stress, narrow and wide channels exhibit different degradation behaviors, with simulations showing a strong electrical field at IGZO near the drain terminal of the main channel, which is unaffected by hydrogen.
Amorphous Titanium Oxide Semiconductors on Quasi-Crystal-Like InGaZnO Channels for Thin Film Transistor Applications
(2015-06)
Hsu, Hsiao-Hsuan
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Chiou, Ping
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Cheng, Chun-Hu
;
Yen, Shiang-Shiou
;
Tung, Chien-Hung
This paper reports an InGaZnO thin-film transistor with titanium-oxide semiconductor as channel capping layer. Based on the experimental results, the titanium-oxide semiconductor has the function of not only a surface passivation layer to reduce the defect states localized at grain boundaries near source/drain contacts, but also a mobility booster to enhance electric field across channel. Compared to control IGZO TFT, the crystalline IGZO TFTs with titanium-oxide semiconductor exhibits an improved performance of a low drive voltage of <5 V, a low threshold voltage of 1.9 V, a low sub-threshold swing of 244 mV/decade, and a high mobility of 13.7 cm(2)/V s. The simple titanium-oxide capping process have been demonstrated in this work, which provides considerable potential for further display applications requiring a low power operation and a low-temperature fabrication.
Correlation of thermal annealing effect, crystallinity and electrical characteristics in c-axis crystallized InGaZnO thin-film transistors
(2015-09-15)
Hsu, Hsiao-Hsuan
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Yen, Shiang-Shiou
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Chiu, Yu-Chien
;
Chiou, Ping
;
Chang, Chun-Yen
A low off-state current of 1.6 x 10(-14) A/mu m and a small subthreshold gate swing of 152 mV/decade were achieved in a novel thin film transistor using a c-axis crystallized InGaZnO semiconductor that could be obtained at a low substrate temperature range of 150 degrees C. From experimental results, we found that the lowered off-state current is mainly attributed to the formation of rich Ga-O bonds to reduce oxygen vacancies, and the c-axis crystallized structure of IGZO to increase the potential barrier on the source side due to the increase of local trap states at the grain boundary. (C) 2015 Elsevier B.V. All rights reserved.
Effect of SiO2 Buffer Layer Thickness on Performance and Reliability of Flexible Polycrystalline Silicon TFTs Fabricated on Polyimide
(2016-12-01)
Chen, Bo-Wei
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Chang, Ting-Chang
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Hung, Yu-Ju
;
Huang, Shin-Ping
;
Chen, Hua-Mao
This letter investigates flexible polycrystalline silicon thin film transistor performance variation due to different buffer layer thicknesses. In flexible electronics, thermal expansion stress during device fabrication is inevitable. A thicker SiO2 buffer demonstrates better endurance to thermal expansion stress from the polyimide substrate during device annealing. However, if the SiO2 buffer thickness is above a critical point, its weak heat dissipation capability causes the optimal ELA crystallization condition to shift. A thermal expansion stress simulation and TEM photos were utilized to verify performance variation. Furthermore, a similar trend was observed in electrical characteristics after negative bias temperature instability.
Structural and electrical characteristics of thin film transistor employing an oriented crystalline InGaZnO channel
(2015-04-01)
Yen, Shiang-Shiou
;
Hsu, Hsiao-Hsuan
;
Chiou, Ping
;
Cheng, Chun-Hu
;
Tung, Chien-Hung
In this study, we investigate the impact of orientated crystalline InGaZnO (IGZO) thin film transistor. To evaluate interface thermodynamic stability of temperature-sensitive IGZO film, the film-structural stabilities of high-and low-indium-content InGaZnO were studied. With increasing annealing temperature up to 700 degrees C, the crystallinity becomes more pronounced while device electrical characteristics are further improved. We find that the apparently reduced off-state current can be attributed to the formation of c-axis-orientated crystalline located at the X-ray diffraction peak of (0, 0, 16). The performance improvements include a very low turn-on voltage close to zero voltage, a small subthreshold swing of 130mV/dec, and a low off-state current of 2.4 x 10(-14)A/mu m at a low operating voltage of 4V. (C) 2015 The Japan Society of Applied Physics
Surface Engineering of Polycrystalline Silicon for Long-Term Mechanical Stress Endurance Enhancement in Flexible Low Temperature Poly-Si Thin-Film Transistors
(2017-04-05)
Chen, Bo-Wei
;
Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Hung, Yu-Ju
;
Huang, Shin-Pin
The surface morphology in polycrystalline silicon (poly-Si) film is an issue regardless of whether conventional excimer laser annealing (ELA) or the newer metal-induced lateral crystallization (MILC) process is used. This paper investigates the stress distribution while undergoing longterm mechanical stress and the influence of stress on electrical characteristics. Our simulated results show that the nonuniform stress in the gate insulator is more pronounced near the polysilicon/gate insulator edge and at the two sides of the polysilicon protrusion. This stress results in defects in the gate insulator and leads to a nonuniform degradation phenomenon, which affects both the performance and the reliability in thin-film transistors (TFTs). The degree of degradation is similar regardless of bending axis (channel-length axis, channel-width axis) or bending type (compression, tension), which means that the degradation is dominated by the protrusion effects. Furthermore, by utilizing long-term electrical bias stresses after undergoing long-tern bending stress, it is apparent that the carrier injection is severe in the subchannel region, which confirms that the influence of protrusions is crucial. To eliminate the influence of surface morphology in poly-Si, three kinds of laser energy density were used during crystallization to control the protrusion height. The device with the lowest protrusions demonstrates the smallest degradation after undergoing long-term bending.