研究發現，以金屬氧化物半導體做為薄膜電晶體通道的材料，像是以氧化銦鎵鋅(InGaZnO)做為電晶體的通道材料，在高電壓、高電流，以及照光操作下的實驗，會造成電晶體的電性劣化，特別是自我加熱效應(self-heating effect)，以及熱載子效應(hot-carrier effect)，都是薄膜電晶體操作時的重要的議題。
在我們做自我加熱效應的實驗研究時，我們觀察在施加很大的閘極及汲極偏壓(SHS)下的電性劣化情形，發現會呈現不對稱的現象。而且自我加熱效應引起的臨界電壓(Vt)往正方向的偏移量會明顯地比只有閘極給偏壓時所造成的偏移量多出許多。並且，我們還觀察到當通道寬度變短時臨界電壓的偏移量會減少；通道長度變短時臨界電壓偏移量便會增加。此外，除了自我加熱操作下的實驗之外，在做基本量測通道電流時，在直流和交流的量測方法下所量到的通道電流值會不一樣。為了研究這些不尋常的劣化現象，我們做了直流自我加熱偏壓、改變交流訊號的自我加熱偏壓、變溫，以及改變偏壓功率……等等的一連串實驗操作，研究種種現象的變化。
另外，對含有蝕刻終止層的經由孔洞接觸主動層雙閘極結構氧化銦鎵鋅薄膜電晶體做熱載子效應操作實驗，討論在上閘極或下閘極施加偏壓下的電壓電流及電容的電性特性曲線劣化情形，結果發現有蝕刻終止層的薄膜電晶體電性特性及劣化現象和沒有蝕刻終止層的薄膜電晶體的特性有很大的不同，因此我們推測特性不同的行為是因為有蝕刻終止層的薄膜電晶體結構會造成有多餘的源極和汲極電極長度遮蔽到上閘極的控制能力。因此，為了證明劣化現象是由薄膜電晶體的結構造成的，藉由改變上閘極的覆蓋長度、元件通道長度、汲極電極長度……等實驗條件，討論含有蝕刻終止層的經由孔洞接觸主動層雙閘結構極氧化銦鎵鋅薄膜電晶體在熱載子效應偏壓下或基本電性量測所造成的影響。
最後，在照光環境下的氧化銦鎵鋅薄膜電晶體在交流及直流偏壓操作下的電性劣化實驗中，討論照光環境下施加偏壓操作的薄膜電晶體現象，由汲極端電容曲線可觀察到電容值有兩階段上升的情形，以及臨界電壓向負方向偏移的現象。所以經由交流及直流偏壓的照光實驗可以釐清劣化現象。

It is found that the metal-oxide semiconductor such as indium-gallium-zinc-oxide thin film transistor under the high current, high bias, and light illumination operation can cause electrical characteristic degradation. Especially, self-heating and hot-carrier effects are very important issues in practical TFT operation.
In the study of self-heating effect, both the asymmetric degradation behavior and more positive Vt shift than that of PGBS are dominated by high gate- and drain-bias operation. Further, Vt shift decreases as the channel width decreases but increases as the channel length decreases. Besides, the channel current under dc-measurement is larger than that under ac-measurement. To investigate these abnormal phenomena, a series of experiments are carried out, such as dc SHS, ac SHS, varied-temperature tress, and varied-power stress, etc.
Moreover, the degradation behavior of hot-carrier effect in via-contact type dual gate IGZO TFT with an etching stop layer is investigated in this study. The characteristic I-V and C-V curves under top/bottom gate bias are discussed. It is found that the hot-carrier effect in TFT with an etching stop layer is different from which without an ESL, and therefore it is inferred that the characteristics are strongly related to device structure, where the TFT with an ESL leads to top gate bias screening by the redundant source/drain electrodes. Accordingly, the various top gate capping lengths, various channel lengths, and varied drain electrode lengths experiment are performed to verify that the redundant source/drain electrodes in the device can affect device characteristics as well as the degradation behavior after HCS.
Finally, in the investigation of illuminated dc and ac bias-stress in InGaZnO thin-film transistors, the effects of illuminated bias stress on characteristics are discussed. There is a hump at the off-state in Cgd curve, and Vt shifts in negative direction after illuminated stress. Moreover, ac/dc-bias stress under light illumination are performed to verify the proposed mechanism.

誌謝…………………………………………………………………………..................iii
摘要………………………………………………………………………….................vii
Abstract………………………………………………………………………………...ix
Figure Caption xiii
Chapter 1 - Introduction 1
1.1 The Progress and Application of Displays 1
1.2 a-IGZO Channel layer for TFT 2
1.3 Motivation 5
Chapter 2 - Parameter Extraction Methodology 14
2.1 The VT extraction method 14
2.2 The subthreshold swing extraction method 15
2.3 The carrier mobility extraction method 16
Chapter 3 - Electrical Characteristic Degradation Mechanisms Induced by Self-Heating Effect 19
3.1 Introduction 19
3.2 Experiment 20
3.3 Results and Discussion 21
3.4 Summary 34
Chapter 4 - Hot-Carrier Effect in Via-Contact Type a-InGaZnO Thin-Film Transistor with an Etching Stop Layer 58
4.1 Introduction 58
4.2 Experiment 60
4.3 Results and Discussion 62
4.4 Summary 73
Chapter 5 - nvestigating Degradation Behaviors Induced by DC and AC Bias-Stress under Light Illumination in InGaZnO Thin-Film Transistors 92
5.1 Introduction 92
5.2 Experiment 93
5.4 Summary 98
Chapter 6 - Conclusion 112

chapter 1
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[10] P. Gorrn, M. Lehnhardt, T. Riedl, and W. Kowalsky, "The influence of visible light on transparent zinc tin oxide thin film transistors," Applied Physics Letters, vol. 91, pp. 193504-193504-3, 2007.
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chapter 3
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chapter 4
[1] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, "Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors," Nature, vol. 432, pp. 488-492, 2004.
[2] E. M. Fortunato, P. M. Barquinha, A. Pimentel, A. M. Gonçalves, A. J. Marques, L. M. Pereira, and R. F. Martins, "Fully Transparent ZnO Thin‐Film Transistor Produced at Room Temperature," Advanced Materials, vol. 17, pp. 590-594, 2005.
[3] H. Yabuta, M. Sano, K. Abe, T. Aiba, T. Den, H. Kumomi, K. Nomura, T. Kamiya, and H. Hosono, "High-mobility thin-film transistor with amorphous InGaZnO4 channel fabricated by room temperature rf-magnetron sputtering," Applied Physics Letters, vol. 89, pp. 112123-112123-3, 2006.
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chapter 5
[1] P. Gorrn, M. Lehnhardt, T. Riedl, and W. Kowalsky, "The influence of visible light on transparent zinc tin oxide thin film transistors," Applied Physics Letters, vol. 91, pp. 193504-193504-3, 2007.
[2] T.-C. Chen, T.-C. Chang, T.-Y. Hsieh, C.-T. Tsai, S.-C. Chen, C.-S. Lin, M.-C. Hung, C.-H. Tu, J.-J. Chang, and P.-L. Chen, "Light-induced instability of an InGaZnO thin film transistor with and without SiO passivation layer formed by plasma-enhanced-chemical-vapor-deposition," Applied Physics Letters, vol. 97, p. 192103, 2010.
[3] P.-T. Liu, Y.-T. Chou, and L.-F. Teng, "Environment-dependent metastability of passivation-free indium zinc oxide thin film transistor after gate bias stress," Applied Physics Letters, vol. 95, pp. 233504-233504-3, 2009.
[4] W.-F. Chung, T.-C. Chang, H.-W. Li, S.-C. Chen, Y.-C. Chen, T.-Y. Tseng, and Y.-H. Tai, "Environment-dependent thermal instability of sol-gel derived amorphous indium-gallium-zinc-oxide thin film transistors," Applied Physics Letters, vol. 98, pp. 152109-152109-3, 2011.
[5] J.-H. Shin, J.-S. Lee, C.-S. Hwang, S.-H. K. Park, W.-S. Cheong, M. Ryu, C.-W. Byun, J.-I. Lee, and H. Y. Chu, "Light effects on the bias stability of transparent ZnO thin film transistors," ETRI Journal, vol. 31, pp. 62-64, 2009.
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