由於使用的方便性，傳統的平面顯示器預估將被可曲撓式顯示器所取代。基於這個原因，研究非晶矽薄膜電晶體(a-Si:H TFT)應用於液晶顯示器時，遭受不同外力產生變形時的可靠度，變的相當重要。
在本論文中，除了探討前述之項目外，亦對非晶矽薄膜電晶體施加AC Stress，來了解當薄膜電晶體同時遭受AC Stress與外力產生的變形時，所產生之影響，試圖模擬薄膜電晶體於實際操作時的情況。
利用金屬薄片上具有不同通道長度及寬度的薄膜電晶體，與以施加單軸方向之壓應力(compressive strain)與張應力(tensile strain)，其施加的方向是平行於源極與汲極電流之方向；探究當遭受外力發生變形時對薄膜電晶體的效能所產生之影響。關於所用之薄膜電晶體的製程過程，最大製程溫度僅達190℃，所呈現之特性為載子遷移率約0.1 cm2/Vs、臨限電壓約1.95 V、漏電流低於10-13 A 。薄膜電晶體的彎曲方式是圓柱型彎曲，有向內彎inward (compression)及向外彎outward (tension)兩種。當施加外力產生變形時，載子遷移率會些微的改變，主要是由於彎曲產生變形時，改變了非晶矽的原始秩序。
本論文中，亦研究當非晶矽薄膜電晶體於彎曲的當下(無論內彎或外彎)，再施加不同AC Stress條件，對其效能的影響。發現到當非晶矽薄膜電晶體處於彎曲並施加AC Stress時，其對元件效能的影響，更勝於無彎曲有施加AC Stress時的情況。

Based on the convenience of the use, the traditional display will be replace by the flexible display. According to this reason, it is very important to study on the reliability of the amorphous silicon (a-Si:H) thin-film transistor (TFT) used in LCD under different mechanical strain. In this research, besides of the above-mentioned we also applied AC stress, to understand the influence of AC stress on an a-Si:H TFT under different mechanical strain.
The influence of mechanical strain on the performance of an hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) with different channel length and width on metal foil substrate under uniaxial compressive or tensile strain was studied, where the strain is parallel to the TFT source-drain current path. The process of TFT with the maximum temperature 190°C exhibited a field-effect mobility of 0.1 cm2/Vs and a threshold voltage of 1.95 V and the leakage current of less than 10-13 A. The TFTs were strained by inward (compression) or outward (tension) cylindrical bending. The mobility had a slightly change under the mechanical strain, which was due to the change in the disorder under bending strain.
We also researched on the influence of uniaxial compressive (tensile) strain on the performance of a-Si:H TFTs under different AC stress conditions. When the a-Si:H TFTs were strained and applied AC stress, we found the performance of a-Si:H TFTs were affected more then the flat ones.

Contents
Chinese Abstract……………………………………….……..i
English Abstract……………………………………………..iii
Contents………………………………………………….…....v
Table Captions……………………………………………...viii
Figure Captions………………………………………………ix
Chapter One - Introduction
1.1 Introduction……………………………………………………….1
1.1.1 Introduction…………………………………………………….1
1.1.2 Hydrogenated Amorphous Silicon…………………………….1
1.1.3 Atomic Structure and the Electron Density of States………….2
1.2 Substrate Materials…………………………………………….....5
1.2.1 Plastic Substrates…………………………………………..…..5
1.2.2 Metal Substrates……………………………………….……….6
1.2.3 Thin Glass Substrates……………………………………….….7
1.3 Defined Bending Direction…………………………………..…..9
Chapter Two - Fabrication
2.1 Deposition of Hydrogenated Amorphous Silicon
by PECVD……………………………………………………….10
2.2 Deposition of SiNx by PECVD………………………………….13
2.3 Deposition of n+ Hydrogenated Amorphous Silicon
by PECVD………………………………………….……………15
2.4 Process Flow……………………………………………………..16
Chapter Three - Apparatus and Parameters
3.1 Apparatus………………………………………………………..17
3.2 Setup instruments for I-V……………………………………....18
3.3 Method of Device Parameter Extraction………………….…...19
3.3.1 Determination of the threshold voltage……………………….19
3.3.2 Determination of the subthreshold swing……………………..19
3.3.3 Determination of the field-effect mobility……………………20
3.4 Density of States…………………………………………………21
Chapter Four - Bending experiment
4.1 Introduction……………………………………………………..23
4.2 Motivation……………………………………………………….24
4.3 Experiments……………………………………………………..25
4.4 Electrical characteristic under mechanical strain…………….26
4.5 Conclusion………………………………………………….……30
Chapter Five - Bending and AC stress experiment
5.1 Introduction……………………………………………………..31
5.2 Motivation……………………………………………………….32
5.3 Experiments……………………………………………………..33
5.4 Results and Discussion………………………………………….34
5.5 Conclusion……………………………………………………….37
Chapter Six - Low temperature experiment
6.1 Introduction……………………………………………………..38
6.2 Motivation……………………………………………………….38
6.3 Experiments……………………………………………………..39
6.4 Electrical characteristic under different temperature…….….40
6.5 Conclusion……………………………………………………….41
References..………………………………………………….42
Tables…………………………………………………….…..50
Figures…………………………………..………….………..52

References
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Chapter Four - Bending experiment
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Chapter Five - Bending and AC stress experiment
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Chapter Six – Low temperature experiment
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