Structural and Electrical Properties of TiO2 Films by Controlled Deposition of Sol-Gel Process
林雅雯、姚品全
E-mail: [email protected]
ABSTRACT
Regarding to the material of high dielectric layers, the characteristic of current leakage is very important, and being worth to study.
However, related works and researches are few, especially in preparation of TiO2 nano thin film by the Sol-Gel method. In this paper, we studied the characteristics of TiO2 nano thin film, with changes the pH value of TiO2 solution formula, heat treatment temperature, film thickness and so on. And the TiO2 was deposited on ITO glass by spin coating, following high temperature furnace tube annealing. Surface morphology and electric characteristic were investigated. The experiment included three parts(i) thin film surface microstructure analysis ; (ii) thin film device measurement ; (iii) thin film optics and penetration coefficient
measurement. TiO2 solution was prepared with titanium (IV) alkane oxygen compound (alkoxide) by Sol-Gel method. It was made from hydrolyzing of titanium-alkane oxide compound and water produced by esterification of acetic acid and IPA. This reaction may reduce the hydrolysis rate of the mellow oxygen compound to avoid fast precipitates, which led to produce homogeneous phase.
By means of the TEM and SEM investigation, Sol-Gel pellets were 15-25nm in size, and the surface was extremely smooth. Brookite structure distinguished XRD. After annealing at 550℃, preferential crystallized texture and structure were formed. Al was taken as the point electrode of thin film device in I-V and C-V measurement. In order to study relation between leakage current, annealing temperature, and film thickness, different annealing temperature(200℃ to 600℃), film thickness and pH value of solution has been involved. As the result, there was a minimum leakeage current 1.2×10-8A with 7.53um thickness (4 layers) after 550℃ annealing. It might be attributed to the better crystallization and smooth surface. On the other hand, we also found that annealing can reduce the leakage current of TiO2 effectively, due to the compensation of oxygen left vacancy during prepare process. Titanium dioxide not only has stable chemical and physical properties, but also has excellent optical property. (photo-conductivity, reflectivity, refractive index and so on. ) Besides, titanium dioxide also has good penetration coefficient. The penetration coefficient of TiO2 thin film is 80% measured by UV-Vis.
Keywords : Sol-Gel ; titanium dioxide ; thin film ; leakage current ; Dielectrics Table of Contents
目錄 封面內頁 簽名頁 授權書... iii 中文摘要... iv 英文摘
要... vi 誌謝... viii 目錄... ix 圖目 錄... xiii 表目錄... xvi 第一章 緒論...
1 第二章 文獻回顧...4 2.1二氧化鈦的製備... 4 2.1.1傳統製程
...4 2.1.1.1氯化法... 4 2.1.1.2硫酸法(sulphate process)... 5 2.1.1.3高溫水解法... 5 2.1.1.4化學氣相沉積法... 5 2.1.1.5氣相冷凝
法... 6 2.1.1.6微乳液法... 6 2.1.2溶凝膠法(Sol-Gel process)...
6 2.2 pH值對溶凝膠的影響 ...10 2.3溶劑的影響... 11 2.4 TiO2簡 介...12 2.4.1二氧化鈦性質與應用...12 2.4.2二氧化鈦結
構... 14 2.5薄膜製程... 15 2.5.1蒸鍍法(Evaporatuon)...
15 2.5.2化學氣相沉積(CVD)... 16 2.5.3反應式濺鍍法 ...17 2.5.4鍍製非晶質的二 氧化鈦薄膜... 17 2.6電容器的基本特性 ...18 2.6.1電容器的頻率特性
...18 2.6.2介電質對電容的影響 ...19 2.6.3介電理論 ...19 2.7漏電流機制簡介 ...20 2.8 光電原理... 21 第三章 實驗方法與量 測... 26 3.1研究方法及實驗流程... 26 3.1.1實驗藥
品...26 3.2實驗步驟 ...27 3.2.1實驗流程
圖...27 3.2.2 TiO2薄膜的製備... ...28 3.2.3 元件測試結構的製作
...29 3.2.4 鋁(Al)上電極的製作 ...30 3.2.5 退火步驟 ...30 3.3 ITO及TiO2薄膜結構與表面特性分析與鑑定... 31 3.3.1膜厚量?... 31 3.3.2 X-Ray繞射分 析 ...31 3.3.3掃描式電子顯微鏡... 32 3.3.4表面平坦度量
測(AFM)... 32 3.3.5拉曼光譜(Raman Spectrum)... 33 3.3.6穿透式電子顯微 鏡... 33 3.3.7光學顯微鏡... 34 3.4 TiO2薄膜光學及電性量測
...34 3.4.1光電導量?... 34 3.4.2紫外-可見光光譜儀... 35 3.4.3 電阻係數量測... ...35 3.4.4 IV漏電流分析(J-E Curve). ...35 3.4.5 C-V
Measurement... 36 3.4.6介電常數(Dielectric Constant)... 36 第四章 結果與討論 42 4.1 TiO2 表面型態分析... 42 4.2 pH對薄膜表面的影響... 42 4.3退火溫度對薄膜的影 響... 43 4.4 XRD分析... 43 4.5拉曼光譜分析... 44 4.6 表面粗糙度的探討(AFM)... 45 4.7片電阻(ρS)... 45 4.7.1未退火的ITO玻璃基 板... 46 4.7.2 500℃退火的ITO玻璃基板... 47 4.7.3 ITO玻璃基板的電阻特
性... 47 4.8 EDX 薄膜成份分析... 48 4.9 TiO2薄膜電性量測...
49 4.9.1 MOS結構和MIM結構的(I-V)漏電特性實驗結 果與比較... 49 4.9.2薄膜厚度的影 響... 51 4.9.3溶液PH值對薄膜的影響... 52 4.9.4退火溫度對薄膜的影
響... 52 4.10厚薄膜影響(TiO2/Si)... 53 4.10.1薄膜厚度... 53 4.10.2漏電流特性... 53 4.10.3介電特性... 53 4.11光電導轉
換... 54 4.12TiO2/ITO Glass吸收度量測... 54 第五章 結 論... 78 參考文獻... 80
REFERENCES
參考文獻 【1】 Fujishma﹐A.Honda﹐“Electrochemical photolysis of water at s semiconductor electrode”﹐Nature﹐238﹐(1972)37 【2】 電 工材料 吳朗 編著 滄海書局 【3】 Takashi Fuyuki and Hiroyuki Matsunami﹐“Electronic Properties of Interface between Si and TiO2 Deposited at Very Low Temperature”Janpanese Journal of Applied Physics﹐25﹐ 1288-1291(1986) 【4】 Takashi Fuyuki and Hiroyuki Matsunami﹐“Electronic Properties of Interface between Si and TiO2 Deposited at Very Low Temperature”Janpanese Journal of Applied Physics﹐25﹐1288-1291(1968) 【5】 G. Blondeau﹐“Influence of Copper Addition on Optical Properties of TiO2”J. Electrochem. Soc.﹐126
﹐1592(1979) 【6】 Hirofumi Takikawa﹐“Properties of titanium oxides film prefared by reactive cathodic vacuum arc deposition” thin Soild Films﹐348﹐169-178(1995) 【7】 K. S. Yeung and Y. W. Lan﹐“A simple chemical vapor depostition method for depoiting thin TiO2 film Thin Solid Films”﹐109﹐169-178(1983) 【8】 H. J. Frenck﹐“Deposition of TiO2 thin film by plasma enhanced decomposition of teraiopropya titanate ”Thin Solid Films﹐201﹐327-335(1991) 【9】 K. S. Yeung and Y. W. Lan﹐“A simple chemical vapor deposition method for depoiting thin TiO2 films”Thin Solid Films﹐109﹐169-178(1983) 【10】 K. S. Yeung and Y. W. Lan﹐“A simple chemical vapor deposition method for depoiting thin TiO2 films”Thin Solid Films﹐109﹐169-178(1989) 【11】 Kiichiro Kamata﹐“Rapid formation of TiO2 films by plasma enhanced decomposition of teraiopropya titanate”Thin Solid Films﹐201﹐327-335(1991) 【12】 Carl. P. Fictorie﹐“Kinetic and mechanistic study of the chemicalvapor deposition of titanium dioxide thin films using tetrakis-(isopropoxo)-tit-nium(IV)”J. Vac.Sci.
Technol.A12﹐1108-1113(1994) 【13】 R. B. van Dover﹐Appl. Phys. Lett.﹐74(20)﹐pp 3041-3043(1999) 【14】 陳繼仁，TiO2陶瓷的燒結
、電性及晶界偏析理論模型之研究，清華大學材料所博士論文(1989) 【15】 W. D. Brown﹐W.W. Grannemann﹐Thin Solid Films﹐51
﹐pp 119-132(1978) 【16】 Yu.D. Dolmatov﹐Priklad﹐Zh.﹐42﹐8﹐(19669)1275 【17】 Z. Jerman﹐Collect. Czech. Chem. Commun.﹐31
﹐(1966)3270 【18】 Yoldas.B.E﹐“Hydrolysis of titanium alkoxide and effects of hydrolytic polycondensation parameters”﹐J.Mater.Sci.﹐21
﹐(1986)1087 【19】 K. Terabe﹐K.Kato﹐H. Miyazaki﹐S. Yamaguchi﹐A. Imai﹐Y. Iguchi﹐“Microstructure and crystallization behaviour of TiO2 Precursor prepared by the sol-gel method using metal alkoxide”﹐J. Mater. Sci.﹐29﹐(1994)1617-1622 【20】 K. P. Kumar﹐and K.
Keizer﹐“Effect of Peptization on Densification and Phase-Transformation Behavior of Sol-Gel-Derived Nanostructured Titania”﹐
J.Am.Ceram.Soc.﹐77(5)﹐(1994)1396-1400 【21】 K. Kamiya﹐S. Sakka﹐“Thermal expansion of TiO2-SiO2 and TiO2-GeO2 glasses”﹐J.
Non-Cryst. Solids.52﹐(1982)357 【22】 J. Livsge﹐S. Doeuff﹐M.Henry and C.Sanchez﹐“Hydrolysis of titanium alkoxides: Modification of the molecular precular precursor by acetic acid”﹐ J. Non-cryst. Solids﹐89﹐(1995)206-216 【23】 R. W. Jones﹐Fundamental principles of sol-gel technology﹐The institute of metals(1989) 【24】 S. Sakka and K. Kamiya﹐“Glasses from metal alcoholates”﹐J. Non-Cryst. Solids
﹐42﹐(1980)40 【25】 Kamiya﹐K. Tanimoto and T. Yoko﹐“Presparation ofTiO2 fibers by hydrolysis and polycondensation of
Ti(O-i-C3H7)4”﹐J. Mater. Sci. Lett.﹐5﹐(1986)402 【26】 J. Livage﹐in“Sol-Gel Science and Technology”﹐eds. by M. A. Aegeter﹐M. Jr.
Jafelicci﹐D.F.Souza and E. D. Zanotto﹐World Scientific﹐Singapore(1989)103 【27】 H. L. M. Pulker﹐G. Paesold﹐and E. Ritter
﹐Refractive indices of TiO2 films produced by reactive evaporation of various titaniunm-oxygen phases APPLIDE OPTICS﹐15.
2986-2991(1976). 【28】 Properties as a Function of Processing Temperature J. Electrochem. Soc. :SOLID-STATE SCIENCE AND TECHNOLOGY﹐119﹐735-739(1972) 【29】 Feng Zhang﹐Highly oriented rutile-type TiO2 films synthesiszed by ion beam enhanced deposition J. Vac. SCI. Technol. A 15﹐1824-1827(1997) 【30】 Kiichiro Kamata﹐Rapid formation of TiO2 films by a conventional CVD method journal of Materials Science Letters﹐9﹐316-319 (1990) 【31】 A. C. Ting and S. Y. Chen﹐J. Appl. Phys.﹐88(8)﹐pp 4628-4633 (2000)
【32】 Mills A. and S. L. Hunte﹐“An overview of semiconductor photocatalysis”﹐J. Photochem. & photobio. A: Chemistry﹐108﹐pp 1-35(1995) 【33】 B. R. Weinberger and R. B. Garber﹐Appl. Phys. Lett.﹐66(18)﹐ pp2409-2411(1995) 【34】 J. D. Deloach and C. R. Aita
﹐J. Vac. Sci. Technol. A﹐16(3)﹐ pp1963-1968(1998) 【35】 O. Carpa,* C.L. Huismanb，A. Rellerb ,Photoinduced reactivity of titanium dioxide ,Progress in Soid State Chemistry 32 (2004) 33-177 【36】 O. Treichel﹐V. Kirchhoff﹐Surface and Coating Technol.﹐123﹐
pp268-272 (2000) 【37】 Jang﹐S. W. Whangbo﹐H. B. Kim﹐K. Y. Im﹐Y. S. Lee﹐ I. W. Lyo﹐and C. N. Whang﹐J. Vac. Sci. Technol. A﹐
18(3)﹐ pp917-921(2000) 【38】 K. Yokota﹐T. Yamada﹐F. Miyashita﹐K. Hirai﹐H. Takano and M. Kumagai﹐Then Solid Films﹐334
﹐pp109-112(1998) 【39】 C. Byun﹐J. W. Jang﹐I. T. Kim﹐K. S. Hong and B. W. Lee﹐ Materials Research Bulletin﹐32 (4)
﹐pp431-440(1997) 【40】 N. Rausch and E. P. Burte﹐J. Electrochem. Soc.﹐140(1)﹐ pp145-149(1993) 【41】 Y. H. Lee﹐K. K. Chan﹐and M. J. Brady﹐J. Vac. Sci. Technol. A﹐13(3)﹐ pp 596-601(1995) 【42】 A. Watanabe﹐Y. Imai﹐Thin Solid Films﹐348﹐pp63-68(1999) 【43
】 T. Kamada﹐M. Kitagawa﹐M. Shibuya﹐and T. Hirao﹐Jhys.﹐30(12B)﹐ pp 3594-3596(1991) 【44】 C. Chaneliere﹐S.Four﹐J. L.
Autran﹐R. A. B. Devine and N. P. Sandler﹐properties of amorphous and crystalline Ta2O5 thin film deposited on Si from a Ta(OC2H5)5 precursor J. Appl. Phys.﹐Vol 83﹐Number9﹐1998﹐p.4823-p.4828 【45】 Wai Shing Lau﹐et al. he Superiority of N2O plasma Annealing over O2 plasma Annealing for Amorphous Tantalum Pentoxide (Ta2O5) Films Jpn. J. Appl. Phys.Vol.3 【46】 M. S. Tsai﹐S. C. Sun﹐and T. Y.
Tseng﹐Effect of oxygen to argen ratio on properties of (Ba﹐Sr)TiO3 thin films prepared by radio-frequencey magnetron sputtering
J.Appl.Phys.82(7)﹐1 October 1997﹐p.3482-p.3487 【47】 陳啟明，以磁控濺鍍法製備二氧化鈦薄膜電容器及電性分析，清華大學電子所 碩士論文(2000)
