臺灣博碩士論文加值系統

論文摘要
隨著液晶平面顯示器科技日新月異, 近年來在液晶平面顯示器已被大眾廣泛的接受而且其應用面也持續的成長中. 主要在於大尺寸顯示器驅動元件技術上更需要更多的技術去改進與改良. 在電子科技工業上一項重要的挑戰, 關於發展全透明光電元件上, 用於主動式液晶顯示器(AMLCDs)中提供一個方法去替代薄膜電晶體裡的非晶矽(a-si)或多晶矽(poly-si), 而使用透明氧化鋅薄膜電晶體可以改善開孔畫素,進而減少功率損耗與避免元件複雜的製作流程, 此外還可做成全透明的電子元件.
本論文研究目的為製造與發展一個高透明薄膜電晶體元件(ZnO-TFT), 在氧化鋅自從發現室溫中氧化鋅在紫外線的行為, 氧化鋅已經變成受吸引的寬能隙半導體材料. 由於氧化鋅是透明材料, 可以利用氧化鋅透明的主要優點, 用在薄膜電晶體(TFT)裡的主動通道層, 去實現透明薄膜電晶體(TTFT).
在於我們實驗研究上結構用Bottom-gate 薄膜電晶體, 把氧化鋅當作主動通道層, 在製程溫度300度與製程壓力30mtorr中用射頻磁控濺鍍沉積氧化鋅. 使用雙層絕緣當作閘極絕緣層 (組成為氮化矽/氧化矽),從實驗可發現, 雙絕緣層可以有效的阻止漏電流使得氧化鋅薄膜電晶體可以成功的動作, 實驗結果可以看出, 本論文製造出氧化鋅薄膜電晶體特性為, 穿透率在70%左右, 為n通道空乏型電晶體的特徵, 所有的實驗結果也可以知道製造透明電晶體, 操作在可見光地方是可行性的, 未來還有很大的發展空間, 相信將來會有更寬廣, 更多采多姿的消費性產品運用.

Abstract
The technological advancement of liquid crystal displays (LCDs) is changing with time everyday. Recently, it has started to dominate the display devices in a large scale and this has urged for more technological improvement. One challenging area for the electronics industry is the development of fully transparent optoelectronics devices. Substituting thin film transistors (TFTs) made of amorphous Si (a-Si) or polycrystalline Si (poly-Si) that are currently used in active-matrix liquid crystal displays (AMLCDs) with transparent ZnO-TFTs would enable improvement in the opening of pixels, resulting in a reduction in power consumption and avoidance of complicated device processing. In addition to that it would result in an all transparent electronics device.
The objective of the present thesis is to fabricate a highly transparent TFT device, with a focus on ZnO-TFT. ZnO has become an attractive wide band gap semiconductor since the demonstration of ultraviolet laser action at room temperature. ZnO can be used as an active channel layer for the realization of transparent thin-film transistors (TTFTs).
In this work bottom-gate-type thin film transistors using ZnO as an active channel layer (ZnO–TFT) have been constructed. The ZnO layers were deposited using rf magnetron sputtering at 300 °C at a working pressure of 30mTorr. A double layer gate insulator consisting of SiO2 and SiNx was effective in suppressing leakage current and enabling the ZnO–TFT to operate successfully. The optical transmittance of ZnO–TFTs fabricated on glass was more than 70% in the visible portion of the electromagnetic spectrum. The prototypical n-channel, depletion mode TFT characteristics, and these results show that it is possible to fabricate a transparent TFT that can even be operated in the presence of visible light. We believe that the consumer application will be further evolved widely based on this development.

Contents
Abstract (In Chinese)
Abstract (In English)
Acknowledgement (In Chinese)
Contents
Chap. 1 Introduction
1-1 Introduction........................................1
1-2 Transparent conductive oxide........................2
1-3 Transparent transistors.............................3
Table-1.................................................6
Reference-1.............................................8
Chap. 2 Basic of deposition instruments and Zinc Oxide
2-1 Plasma Enhanced Chemical Vapor Deposition(PECVD)...10
2-1-1 Process principles..............................10
2-2 Reactive sputtering (Berg’s model)................13
2-2-1 Rate equations for partial pressure of reactive gas.....................................................14
2-2-2 Rate equations at target and substrate surfaces.16
2-2-3 Sputtering rate and equilibrium for surface kinetics................................................17
2-3 Zinc Oxide.........................................18
2-3-1 Introduction of ZnO.............................18
2-3-2 Basic properties of ZnO.........................19
2-3-3 Electrical properties of ZnO....................19
2-3-4 Photoconductivity of ZnO........................20
Figure-2...............................................23
Table-2................................................25
Reference-2............................................29
Chap. 3 Characterization of thin film and devices
3-1 Thin film characterization.........................31
3-1-1 Optical transmission and bandgap of thin film...31
3-1-2 Conductivity, mobility, and carrier concentration37
3-2 Device characterization............................39
3-2-1 DC current-voltage measurements.................39
3-2-2 Thin film transistor mobility and threshold voltage extraction..............................................40
Reference-3............................................44
Chap. 4 Experimental details
4-1 Zinc Oxide.........................................46
4-2 Gate insulator layer...............................47
4-3 Fabrication of ZnO-TFT.............................48
Figure-4...............................................50
Table-4................................................52
Chap. 5 Results and discussions
5-1 Characteristics of the ZnO films...................54
5-2 Reduction of the leakage current through the gate insulator...............................................55
5-3 Characteristics of the ZnO-TFT.....................56
Figure-5...............................................57
Chap. 6 Conclusion......................................71

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