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博碩士論文 etd-0801106-145749 詳細資訊
Title page for etd-0801106-145749
論文名稱
Title
非晶矽薄膜電晶體光漏電流與電性物理機制之研究
Investigation on Photo Leakage Current and Electrical Mechanism of a-Si Thin Film Transistor
系所名稱
Department
畢業學年期
Year, semester
語文別
Language
學位類別
Degree
頁數
Number of pages
94
研究生
Author
指導教授
Advisor
召集委員
Convenor
口試委員
Advisory Committee
口試日期
Date of Exam
2006-07-06
繳交日期
Date of Submission
2006-08-01
關鍵字
Keywords
光漏電流、薄膜電晶體
photo leakage current, thin film transistor
統計
Statistics
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The thesis/dissertation has been browsed 5670 times, has been downloaded 5129 times.
中文摘要
拜科技之賜,顯示器由傳統的陰極射線管CRT進步到液晶顯示器LCD,非晶矽薄膜電晶體極多晶矽薄膜電晶體已經用於製造液晶顯示器的畫素開關,尤其是非晶矽薄膜電晶體更是已經大量用於製造大面積的顯示面板。
在製作a-Si TFT的主動層時,有兩個主要改進的目標:增加其場效mobility及降低其在背光源照射下的漏電流;增加其場效mobility是為了用於大面積高解析度的面板,另外一方面因為a-Si的光導係數較高因此在光照射下會有較大的漏電流,當面板應用於須以強背光照射的產品如多媒體顯示器、液晶電視時光漏電流就會造成顏色顯示上的問題。
在TFT導通時,電荷會經由TFT儲存於液晶電容及輔助電容中,在TFT關閉後利用上述兩個電容所產生的電壓使液晶轉動,因為電視每秒顯示30張畫面,因電容的電壓必須維持定值至少1/30秒,光漏電流過大會造成TFT在關閉時仍有通道讓電荷通過,電容中的電荷就會由此通道流失,所提供的電壓就會減少,造成液晶旋轉的角度不足,所顯示的顏色不準確。
鑑於此,本論文將研究薄膜電晶體在背光源照射下,所產生的電性變化,探討在製作主動層時通入不同流量的SiF4是否會對光漏電流有所影響。發現主動層製程中通入了SiF4,造成了主動層偏P型半導體及增加了主動層的缺陷密度,因此對光漏電流的抑制效果也越好。
Abstract
The hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) have been widely used as switching device for large-area electronics such as active matrix liquid crystal displays (AM-LCDs). a-Si TFT is particularly advantageous to the production of large screen displays and facilitates mass production.
When employing an a-Si:H layer, the main objectives are to enhance the field effect mobility and to reduce the off-state current under light illumination. The increase of field effect mobility results in wide application of a-Si:H TFTs in high resolution LCDs. On the other hand, a-Si:H has high photoconductivity which results in high off-state current of a-Si:H TFT under light illumination. The off-state leakage current under light illumination is, in particular, a serious problem in the projection and/or multimedia displays that require high intensity backlight illumination.
Minimizing the off-current increase by a-Si photosensitivity is an important design consideration for achieving highimage-quality LCDs. TFT off-current increase by photoillumination of a-Si decreases the charge stored on the pixel during the TFT off-time, and results in gray-scale shading, flicker, crosstalk and other display nonuniformity in the LCD.
The fluorine incorporated amorphous silicon [a-Si:H(:F)] and amorphous silicon (a-Si:H) were illuminated with backlight to investigate electrical characteristics. The effect of different [SiF4] / [ SiH4] ratio on the performance of a-Si:H(:F) TFTs was also studied. We found the density of states in the gap of a-Si:H(:F) will be modified by the introduction of F into a-Si:H and resulting the shift of the Fermi level toward the valence band edge. The density-of-states increasing cause more recombination centers for electrons and holes to increase the carrier recombination rate. The shift in the Fermi level leads to a reduction of the photoconductivity of a-Si:H(:F). Due to these two important factor, the photo leakage current decreases.
目次 Table of Contents
Chinese Abstract……………………………………………i
English Abstract……………………………………………iii
Chinese Acknowledgment……………………………………v
Content……………………………………………………vii
Table Captions………………………………………………x
Figure Captions……………………………………………xi
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 Photo leakage current mechanism………………………5
1.3 Some solutions for reducing photo leakage current………9
Chapter Two - Fabrication
2.1 Deposition of Hydrogenated Amorphous Silicon
by PECVD………………………………………………………11
2.2 Deposition of SiNx by PECVD…………………………………14
2.3 Deposition of n+ Hydrogenated Amorphous Silicon
by PECVD………………………………………………………16
2.4 Process Flow……………………………………………………17
Chapter Three - Apparatus and Parameters
3.1 Apparatus………………………………………………………18
3.2 Set up instruments for I-V……………………………………19
3.3 Method of Device Parameter Extraction……………………20
3.3.1 Determination of the threshold voltage………………21
3.3.2 Determination of the subthreshold swing………………21
3.3.3 Determination of the field-effect mobility……………21
3.4 Density of States………………………………………………22
Chapter Four –Backlight Illuminated experiment
4.1 Introduction……………………………………………………24
4.2 Motivation………………………………………………………25
4.3 Experiments……………………………………………………26
4.4 Electrical characteristic under backlight illumination……27
4.5 Conclusion………………………………………………………31
Chapter Five - Activation Energy Measurement experiment
5.1 Introduction……………………………………………………32
5.2 Motivation………………………………………………………33
5.3 Experiments……………………………………………………34
5.4 Results and Discussion…………………………………………35
5.5 Conclusion………………………………………………………39
Chapter Six - Double Layer Structure Measurement
5.1 Introduction……………………………………………………40
5.2 Motivation………………………………………………………41
5.3 Experiments……………………………………………………42
5.4 Results and Discussion…………………………………………43
5.5 Conclusion………………………………………………………45
References…………………………………………………46
Tables………………………………………………………55
Figures……………………………………………………57
參考文獻 References
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Chapter Two - Fabrication
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Chapter Three - Apparatus and Parameters
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Chapter Four - Backlight Illuminated experiment
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4. J. S. Byun, H. B. Jeon, K. H. Lee, and J. Jang, “Effect of Cl incorporation on the stability of hydrogenated amorphous silicon,” Appl. Phys. Lett., vol. 67, pp. 3786–3788, 1995.
5. W. B. Jackson and N. M. Amer, Phys. Rev. B 25, 5559 (1982).
6. Sandrine Martin, Jerzy Kanicki, Nicolas Szydlo, Alain Rolland “Analysis of the amorphous silicon thin film transistors behavior under illumination” AM-LCD ‘97
7. W. E. Spear, J. Non-Cryst. Solids 59/60, 1 (1983)
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Chapter Five - Activation Energy Measurement experiment
1. F. B. Ellis, Jr., R. G. Gordon, W. Paul, and B. G. Yacobi, J. Appl. Phys. 55, 4309 (1984).
2. J. K. Yoon, Y. H. Jang, B. K. Kim, H. S. Choi, B. C. Ahn, and C. Lee, J. Non-Cryst. Solids 164-166, 747 (1993).
3. M. Akiyama, T. Kiyota, Y. Ikeda, T. Koizumi, M. Ikeda, and K. Suzuki, SID 95 Digest (Society for Information Display, Florida, 1995), p. 158.
4. W. B. Jackson and N. M. Amer, Phys. Rev. B 25, 5559 (1982).
5. R. S. Muller and T. I. Kamins, Device Electronics for Integrated Circuits 2nd ed. (Wiley, New York, 1986), p. 427.
6. T. Globus, H. C. Slade, M. S. Shur, and M. Hack, “Density of deep bandgap states in amorphous silicon from the temperature dependence of thin film transistor current”, Mat. Res. Soc. Proc., vol.336,pp.823,1994.
7. Dosi Dosev, Josep Pallares and Joaquim Puigdollers, “Fabrication, Characterisation and Modelling of Nanocrystalline Silicon Thin-Film Transistors Obtained by Hot-Wire Chemical Vapour Deposition”, p. 64.
8. M. S. Shur, M. D. Jacunski, H. C. Slade, and M. Hack, “Analytical Models for Amorphous-silicon and Poly-silicon Thin-film Transistors for High-definition-display Technology, ” J. of the SID, 3-4, 223 (1995)
9. W. E. Spear, J. Non-Cryst. Solids 59/60, 1 (1983)



Chapter Six - Double Layer Structure Measurement
1. F. B. Ellis, Jr., R. G. Gordon, W. Paul, and B. G. Yacobi, J. Appl. Phys. 55, 4309 (1984).
2. J. K. Yoon, Y. H. Jang, B. K. Kim, H. S. Choi, B. C. Ahn, and C. Lee, J. Non-Cryst. Solids 164-166, 747 (1993).
3. M. Akiyama, T. Kiyota, Y. Ikeda, T. Koizumi, M. Ikeda, and K. Suzuki, SID 95 Digest (Society for Information Display, Florida, 1995), p. 158.
4. M. S. Shur, M. D. Jacunski, H. C. Slade, and M. Hack, “Analytical Models for Amorphous-silicon and Poly-silicon Thin-film Transistors for High-definition-display Technology, ” J. of the SID, 3-4, 223 (1995)
5. W. E. Spear, J. Non-Cryst. Solids 59/60, 1 (1983)
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