Browsing by Author "Chen, Yi-Heng"

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Effect of interfacial layer on device performance of metal oxide thin-film transistor with a multilayer high-k gate stack
(2018-08-30)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Kuo, Po-Yi
;
Yu, Min-Chin
The amorphous indium gallium zinc oxide thin-film transistors (TFTs) with a multilayer high-k gate stack are investigated in this research. In order to achieve a high quality gate insulator for plastic flexible display application, the multilayer high-k gate stacks (SiO2/TiO2/HfO2) are deposited by a low-temperature physical vapor deposition (PVD) process. On the other hands, an interfacial layer between the high-k stack and metal oxide channel is important for the device performance. The effects of interfacial layer material (SiO2 or Ga2O3) are also discussed in this report. The devices with SiO2 interfacial layer show a high on/off current ratio of similar to 7x10(7) for its low gate leakage current, a small sub-threshold swing of 0.093 V/decade and a high field-effect mobility of similar to 37.8 cm(2)/Vs for its good interface condition and low interface defeats. This research shows that the interface engineering of multilayer PVD gate stacks is necessary for oxide TFT fabrication.
Investigation of low operation voltage InZnSnO thin-film transistors with different high-k gate dielectric by physical vapor deposition
(2018-08-30)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
;
Kan, Kai-Zhi
;
Yu, Min-Chin
Amorphous Indium-Zinc-Tin-Oxide thin-film transistors (a-IZTO TFT) using different types of high-k materials (like HfO2, ZrO2 and Al2O3) as gate dielectric are studied in this work. All gate dielectric films were deposited by physical vapor deposition (PVD) process for better composition control. Compared with the traditional SiO2 gate insulator, a high-k gate dielectric can reduce the operation voltage of TFT device significantly. The TFT device with ZrO2 gate insulator exhibits a small subthreshold swing of 0.126 V/decade, high field-effect mobility of similar to 40.7 cm(2)/Vs, low threshold voltage of -0.05 V, and large On/Off current ratio of similar to 1.01 x 10(7). The mechanisms for electrical improvements are also investigated. These results demonstrate the potential application of PVD-deposited ZrO2 thin film as a promising gate dielectric in oxide-based thin-film transistors.
Performance improvements of tungsten and zinc doped indium oxide thin film transistor by fluorine based double plasma treatment with a high-K gate dielectric
(2018-11-01)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
;
Yu, Min-Chin
;
Gan, Kai-Jhih
The electrical characteristics and XPS analysis for the amorphous tungsten and zinc doped indium oxide thin film transistor, which was performed with single or double different fluorine based remote plasma treatment, were investigated in this study. A high mobility TFT device with the tungsten doped channel was fabricated in the previous study, but there was an inevitable negative shift for the threshold voltage, which will be a limit for the application of systemic circuit design. Therefore, a double fluorine based remote plasma treatment process is proposed for the high electronegativity of fluorine element and its similar radius as oxygen, which can be used to terminate the donor-like oxygen vacancy. It may induce a positive shift of threshold voltage, while carrier concentration and field effect mobility might be maintained. As a result, the sample with CF4/N-2+O-2 plasma treatment exhibits a higher on/off current ratio of similar to 4.73 x 10(6), a lower sub-threshold swing value of 0.070 V/decade, and a lower interfacial trap density value of 5.21 x 10(11) eV(-1) cm(-2) than other samples, while there is even a desirable positive shift of threshold voltage and acceptable field effect mobility of 31.2 cm(2)/Vs. This research proposes an effective approach to improve the reliability characteristic and adjust the inevitable negative shift of threshold voltage without sacrificing the carrier mobility of device.
Photoresponsivity Enhancement and Extension of the Detection Spectrum for Amorphous Oxide Semiconductor Based Sensors
(2019-03-01)
Ruan, Dun-Boo
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Liu, Po-Tsun
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Chen, Yi-Heng
;
Chiu, Yu-Chuan
;
Chien, To-Chun
In this study, indium gallium zinc oxide (InGaZnO [IGZO]) active layer capped with an ultrathin p-type stannous oxide (SnO) is demonstrated to be a thin film transistor (TFT) for color scanning and photosensing device applications. Typically, the sole IGZO-based TFT is blind to visible light and hard to be developed for visible light sensing. The combination of IGZO and SnO layers can extend the light detection spectrum into visible light wavelengths and ameliorate the photosensing characteristics. The optical responsivity and signal to noise ratio can even be enhanced from 1.05 x 10(-2) to 398.02 A W-1 and from 2.1 x 10(1) to 6.8 x 10(5) with at least four orders of magnitude, respectively. With the detailed material analysis and physical model discussed, it suggests that the large amount of additional light-excited carrier generated in the capping layer is the key factor for the significant improvement. Furthermore, the phenomenon of persistent photoconductivity can be effectively suppressed by its natural recombination under the heterojunction structure without applying charge-pumping method. The electrical uniformity of the sensor device is also highly potential for the next-generation displays integrating the photosensing functions.
The influence on electrical characteristics of amorphous indium tungsten oxide thin film transistors with multi-stacked active layer structure
(2018-11-30)
Ruan, Dun-Bao
;
Liu, Po-Tsun
;
Gan, Kai-Jhih
;
Chiu, Yu-Chuan
;
Yu, Min-Chin
In order to effectively enhance the carrier mobility and device stability, simultaneously, a multi-stacked active layer of thin film transistor with a novel type of channel material, amorphous indium-tungsten-oxide, is proposed in this work. Atop-cappingoxygen-rich indium-tungsten-zinc-oxide thin film is used for suppressing the influence of the molecular adsorption or desorption from the ambient at the back channel in the gate bias stress test. In addition, a bottom-bufferingoxygen-rich indium-tungsten-zinc-oxide thin film is deposited to avoid the oxygen vacancy generation during the following thermal process. On the other hand, a 1-nm thick WO3 film is inserted between the high-k gate insulator and active layer, which play important roles as interfacial layer for improving the interface quality and keeping the stability of front channel film. Besides, an HfO2 dielectric film is chosen as gate insulator for realizing the low-voltage operation. As a result, the novel tungsten doped channel material with both-sideoxygen-rich active layer exhibits a high I-ON/I-OFF current ratio of similar to 6x10(7) for low gate leakage current, attributing to the Atop-cappingoxygen-rich thin film. Then, a high field-effect mobility of similar to 27.9cm(2)/V.s and a low sub-threshold swing of 0.079 V/decade are achieved by the good interface quality. This structure with both-sideoxygen-rich active layer exhibits its potential application for the future high-resolution and large-size display manufacture.