透明氧化鋅之薄膜電晶體技術開發研究
研究生：鄒一德
指導教授：劉柏村 博士
國立交通大學
光電工程系
顯示科技研究所
中文摘要
本 研 究 論 文 成 功 地 發 展 出 一 套 新 式 具 有 高 透 光 性 ( Highly
transparent )、高載子移動率( High mobility )的氧化鋅( Zinc Oxide )透
明薄膜電晶體( ZnO-Transparent Thin Film Transistors )，可應用於主動
式顯示面板( Active Matrix Liquid Crystal Display )技術及搭配有機發
光二極體面板( Organic Light Emitter Diode Panel )作為驅動電路，以
增大顯示電晶體元件的效能與顯示畫素開口率，並減緩光漏電(Photo
leakage current)對元件造成這影響。亦可推廣應用至驅動電路，達成
系統面板整合技術( System On Panel )的遠景。在研究中，我們利用交
大半導體中心之直流濺鍍機台( DC Sputter )，使用 4 吋金屬鋅( Zinc )
的靶材( Target )，改變不同的直流濺鍍功率，於矽晶元基板上形成最
具均勻性之薄膜，並藉由調配不同鋅原子與氧原子的組成比例，來形
I成具備透明與半導體特性之氧化鋅薄膜；藉由在濺鍍過程時，改變通
入氧氣的流量及製程完成後的後續退火處理，我們成功建立一個得以
在室溫環境之下，均勻氧化鋅薄膜的沈積且具有最佳薄膜電晶體電性
表現的半導體層( Semiconductor layer )沉積條件。在本論文中，我們
也利用各種材料分析技術與儀器，如紅外線光譜儀( FTIR ), X 光薄膜
繞 射 儀 ( XRD ) 等 ... 來 針 對 氧 化 鋅 半 導 體 薄 膜 之 結 晶 性
( Crystallization )、晶格尺寸( Grain size )、薄膜厚度( Thickness )和薄
膜表面( Surface morphology )等特性進行分析與研究，並對氧化鋅薄
膜製程電晶體元件，進行電晶體元件電性特性的分析與探討。
Investigation on Thin-Film-Transistors with a
Transparent Material Zinc-Oxide Layer
Student：Yi-Teh
Advisor：Dr. Po-Tsun Liu
Display Institute & Institute of Electro-Optical Engineering,
National Chiao Tung University
Abstract
In this thesis, we have successfully developed a transparent thin film transistors (TTFT) using a novel material Zinc Oxide (ZnO) as semiconductor layer, with high carrier mobility and optical transparency. The use of ZnO-based material can increases the field-effect mobility of TFT devices, the aperture of AMLCD panel and releases the issue of photo-excited leakage current. In this work the ZnO film was deposited on a silicon substrate by sputtering Zinc metal target in DC glow discharge plasma of an argon/oxygen mixture. We changed the power of DC sputter to adjust the uniformity of the ZnO film. Also, the conductivity and carrier concentration were controlled by adjusting the flux of the mixture oxygen during film deposition and thermal annealing temperatures. An optimal ZnO film deposition condition was finally established at room temperature for the ZnO TFTs. The benefit of using the DC sputter system possesses the feasibility and varieties to easily adjusting the optimal rate of Zn/ZnO mixture, Zn1+xO, and ZnO for TFTs.
Several material analysis techniques, such as FTIR, XRD, and etc. were III
utilized to discussing the crystallization, grain size, and surface morphology of ZnO films. Electrical characteristics and conduction mechanisms of ZnO TTFT devices were also investigated by I-V characteristic analysis.
誌謝
轉眼間，還沉浸在大學畢業的歡愉之中時，精采且短暫的兩年碩士班生涯， 悄悄的過去了。在這兩年之中，除了感謝生我、養我、使我在學識養成的路上， 無需擁有任何生活必需上壓力，並在我無助時，提供我最好避風港的父母親外， 亦深深地感謝我的指導教授 劉柏村老師，在學術研究、知識、人格養成上不斷 地給予指導、教誨與提攜。也深刻感謝共同研究團隊，中山物理教授 張鼎張老 師，在生活及待人處事方面給予的幫助與啟發，使我收穫良多並更加成長，在此 對兩位老師致上最深的敬意與感謝。 此外，我還要感謝主要指導、引領我研究方向的 黃震鑠學長，使我能順利 完成此篇論文研究。還有 吳興華、蔡志中、王敏全、李泓緯、黃士哲、高世欽 等諸位學長，謝謝你們在我遇到困難時的鼓勵與協助，並在實驗瓶頸上指引方 向，在每一個感覺孤立無援的時候，能給我許多寶貴的經驗和協助。也要感謝於 一起努力的好伙伴：俊榮學長、世青學長、齊冠學長、宗晟、彥伯、承鴻、淵舟、 皓麟等，由於你們的陪伴，不僅於研究、實驗上，在其他相處的時間中，也給了 我許多歡樂，和感動的回憶；還有可愛的學弟們：千睿、祟維，不論實驗上與生 活中的相伴與提供種種的經驗與幫助。也感謝我的前女友 芷筠，在我碩二下學 期最艱苦的日子中的包容與相陪，為我倆劃下彩色漂亮的句點。 最後，感謝國家奈米元件實驗室(NDL)提供良好的環境與設備，使我能順利 V完成我的實驗。也感謝 城中扶輪社以及我的贊助人 詹仁道總裁，在短短的兩年 之中，給予我的種種肯定，頒予我極高榮譽的扶輪獎學金，使我碩班的歲月中， 得以減輕帶給父母親經濟上的壓力，得以心無旁鶩地專心於研究上面。僅以此論 文獻給我的父母，以及一路上每一位幫助過我的學長、同學、學弟們。 一德 2006.06 VI
Contents
ABSTRACT(CHINESE)
... I
ABSTRACT(ENGLISH)
... III
ACKNOWLEDGEMENTS...V
CONTENTS
...VII
TABLE CAPTIONS
……….……IX
FIGURE CAPTIONS
……….………..X
CHAPTER 1. INTRODUCTION
1-1 General Background
... 1
1-2 Motivation
………...2
CHAPTER 2. EXPERIMENTAL PROCEDURES
2-1 Transparent Conductive Oxide
... 5
2-1-1 Indium Tin Oxide
………...6
2-2 TFT Fabrication
... 7
2-3 Experimental Procedures
... 9
2-4 Methods of Depositing ZnO Films
……….10
2-4-1 Changing of DC Power in Sputtering System
…10
2-4-2 Adjusting The Rate of Argon And Oxygen
……..11
2-4-3 Patterning
………11
2-4-4 Changing Annealing Temperature
………..12
2-4-5
Changing
Annealing
Pressure……….14
CHAPTER 3 RESULTS AND DISCUSSIONS
3-1 ITO Film Analysis
... 15
3-2 ZnO Film Analisys
... 15
3-2-1The XRD Measurement of ZnO Films
... 17
3-2-2 The FTIR Measurement of ZnO Films
... 16
3-3 The Electrical Characteristics of ZnO based TFTs
... 17
3-3-1 Annealing in room pressure states
... 17
3-3-2 Annealing in high vaccum states
... 18
3-3-3 Annealing with oxygen flow
... 19
CHAPTER 4 CONCLUSION
REFERENCES
... 23
FIGURES AND TABLES
Table Caption
Chapter 1
Table 1 There are some properties of Transparent Conducting Oxides at room temperature
Chapter 2
Table 2 Experimental Flow Path
Table 3 Conditions of the DC power we applied
Table 4 Experimental conditions of different ( Argon / Oxygen ) mixture ratio Table 5 Etching solution list
Figure Captions
Chapter 1
Figure1-1 Motivated Transparent Thin Film Transistor device
Chapter 2
Figure 2-1 Assumed band structure of (a) un-doped and (b) Tin-doped In2O3
Figure 2(a) Schematically illustrated cross-sectional ZnO-based TFTs
Figure 2(b) Schematically illustrated top-view ZnO-based TFTs
Figure 3 Schematic diagram of DC sputter system
Chapter 3
Figure 3 Shows the system of DC sputter.
Figure 3-1 Shows the resistance of different flow of oxygen.
Figure 3-2 Shows the relationship with different annealing temperature and
resistance.
Figure 4 Illustrates the measurement of as-deposited ZnO film on a single
crystalline Silicon substrate (100) with different argon and oxygen mixture.
Figure 5 Illustrates the measurement of ( argon / oxygen ) ratio ( 24 / 4 ) samples
annealed in different temperature.
Figure 6 The comparison of different Argon / Oxygen rate in FTIR.
Figure 7 The comparison of different annealing temperature in FTIR.
Figure 8 The ID-VG of our TTFTS in 500℃ annealing condition with Room
Pressure Annealing Furnace.
Figure 9 The ID-VD of our TTFTs in 500℃ with Room Pressure Annealing
Furnace.
Figure 10 The ID-VG of ZnO-based TFTs in 300℃、400℃、500℃ with Vacuum
Annealing Furnace annealing.
Figure 11 The ID-VD of our TTFTs in 300℃ annealing conditions.
Figure 12 The ID-VG of the ZnO-based TFTs annealing in 0.05 mtorr, 0.1mtorr,
0.15 mtorr, and 0.2 mtorr with Vacuum Annealing Furnace.
Figure 13 The relationship between annealing pressure and mobility change.
