近年來,薄膜電晶體包含主動層為非晶矽或多晶矽已經被廣泛應用在液晶顯示器(LCD)的畫素驅動元件。尤其，非晶矽(a-Si:H)在大尺寸面板以及大量製造上的優勢。
但是非晶矽有高的光敏感性，在光線照射下將導致高光致漏電。尤其，在光線照射下的高漏電流將是依個很嚴重的問題因為投影顯示器下需要更強的背光模組。隨著解析度的增加，薄膜電晶體的效能也必須隨著增加，才能符合每次充電的時間越來越短。薄膜電晶體的效能包含了ON電流，OFF電流，臨界電壓等
在者，在平面顯示器，改善薄膜電晶體的有效電子遷移率，已經朝向整合電路，而再結晶技術產生多晶矽已經成為潮流。然而雷射再結晶技術遭受到高成本、製程複雜、在大尺寸上的不均勻性的影響。所以，取而被強力渴望的是直接沉積的高品質低溫多晶矽的前途將大有可為。
本論文中，我們將利用高密度電漿系統直接沉積多晶矽技術，製造薄膜電晶體。而且透過電漿處理改善元件特性。並且透過照光實驗，證實對直接沉積多晶矽對光漏電有明顯抑制的效果，對於面板越來越強的背光模組有正面的幫助。而透過電壓以及電流的壓力測試，元件的可靠度得到了證實。而元件在電性方面直接沉積多晶矽的元件亦表達出優越的有效電致遷移率，而高性能的表現更能應用在大尺寸主動示陣列液晶顯示器上(AMLCD)或者主動示陣列有機發光二極體顯示器(AMOLED)技術中。

In recently yesrs,Thin-film transistors (TFTs) including an active layer of amorphous silicon or polycrystalline silicon have been widely employed as the pixel-driving elements of a liquid crystal display (LCD). Particularly, a-Si:H TFT is advantageous to the production of large screen displays and facilitates mass-production.
a-Si:H has high photoconductivity which results in high off-state leakage currents of a-Si:H TFT under light illumination . Particularly, the off-state leakage current under light illumination is a serious problem in the projection and/or video displays which require high intensity backlight illumination.As the resolutions is higher , the TFT’s performance must be higher to achieve the short charge time each line can charge. The performance includes mobility ,on current, off current, photo leakage current, threshold voltage ,and subthrehold swing.
Furthermore, the to improve the mobility of thin-film transistors (TFT) to enable total integration of peripheral electronics in flat panel displays and imagers has led to recrystallized polycrystalline silicon (poly-Si) as the material of choice.
However, laser recrystallized polycrystalline silicon suffers from high cost , complex processing, and significant nonuniformity over a large area. Indeed, the direct deposition of good-quality low-temperature poly films is highly desirable and constitutes a promising alternative.
In this thesis, we use HDPCVD to fabricate direct deposition poly-TFT successfully.Through plasma passivation, we improve the characteristic of device. The photo-Leakage current have been reduced obviously to our device under light illumination, and is benefit to higher intensity light of large screen display. And our TFT device exhibits stable characteristics with voltage and current stress , and it’s also confirmed that the device is reliable. On the characteristic of device, the direct-deposited poly TFT device exhibits higher effective carrier mobility than that of conventional one. For that reason, the high performance provides the potential of the direct-deposited poly TFT to apply for AMLCD and AMOLED technology.

Contents

Abstract(Chinese)……………………………………………………..I
Abstract(English)……………………………………………………..III
Content………………………………………………………………..IV
Table Captions………………………………………………………..VI
Figure Captions…………………………………………………….....VII

Chapter:1 introduction
1.1General background ……………………………………...…1
1.2Motivation…………………………………………………...2
1.3Organization of This Thesis…………………………………3

Chapter:2 High performace tft
2.1 Operation method &device requirement……………………5
2.2 Discussion of photo leakage current mechanism ………......6
2.3 Solution for Ion---Transfer Line Method ……………………7
2.4 Solution for Ioff………………………………………………8

Chapter:3 Fabrication of high performance tft
3.1 HDPCVD………………………………………….………10
3.1.1 Introduction ……………………………………...….10
3.1.1 HDPCVD direct deposition……………………..…...11
3.1.2 HDPCVD BEN method……………………………...11
3.3 Determination of poly Si…………………………………..12
3.3.1 TEM analysis...............................................................12
3.3.2 RAMAN analysis........................................................12
3.4 Device fabrication flow……………………………………13
3.5 summery…………………………………………………...14

Chapter:4 Result characteristics analysis and discussion
4.1 HDPCVD condition 1……………………………………..15
4.1.1 Device characteristics with SiF4………………….…15
4.1.2 Plasma passivation improve device characteristic…..15
4.1.3 Device photo leakage current………………………..16
4.2 HDPCVD condition2 optimized condition………………...16
4.2.1 Device characteristic without SiF4…………………..17
4.2.2 Device characteristic after passivation …………...…17
4.2.3 Device characteristic after photo current test………..18
4.3 Voltage stress………………………………………………18
4.4 Current stress………………………………………………19
4.5 Summary……………………………………………..……20

Chapter: 5Conclusion …………………………………………………..21

References………………………………………………………………22

Reference

Chapter1
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Chapter2
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Chapter3
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Chapter4
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