近年來，超大型積體電路採用高介電材料取代二氧化矽做為動態記憶體中電容之介電材料已有增加的趨勢。隨著高密度動態記憶體中電荷儲存結構尺寸之縮減趨向，二氧化鈦與鈦酸鋇由於具有高介電常數、高折射係數和高化學穩定性，故有希望應用於高密度動態記憶體之介電材料。我們採用冷壁、水平式之有機金屬化學氣相沈積法成長二氧化鈦與鈦酸鋇薄膜於矽(100)、砷化鎵(100)、磷化銦(100)及氧化鎂(100)基板， 並將成長溫度在280℃與750℃之間作調變。使用的原料為Ti(i-OC3H7)4、Ba(DPM)2、笑氣與氧氣。二氧化鈦與鈦酸鋇薄膜之成長速率及組成結構受基板溫度與生長氣壓等因素影響。 我們使用 X-ray 繞射分析二氧化鈦之相轉換特性，X-ray繞射結果顯示在不同基板成長之二氧化鈦具有相同之相轉換溫度(450℃)。 單相rutile結構可在450℃以上成長於磷化銦基板； 而單相anatase結構可在450℃以下成長於氧化鎂基板。二氧化鈦之光電特性與其薄膜結構相關。單相rutile(110)結構在500℃以上之成長溫度於磷化銦基板上獲得；同相之anatase(100)結構亦可在300℃與375℃之間成長於氧化鎂(100)基板。另一方面，生長溫度及氧化劑對鈦酸鋇薄膜之電特性與結構造成之影響亦將詳細討論。
然而。二氧化鈦與鈦酸鋇薄膜具有柱狀結構，此結構造成漏電流的路徑，導致介電常數之降低。我們使用熱退火改善二氧化鈦薄膜之結晶特性，介電常數經由熱退火處理後增加至110.08；而漏電流亦可減少至5×10-5 A/cm2。未來期望能朝向改進薄膜之結晶特性的目標前進。

In recent years, there has been increasing demands for high dielectric materials to replace SiO2 for high-density dynamic random access memories with ultra large scale integration (ULSI). As the dimensions of the charge storage node decrease in high-density dynamic random access memories (DRAMs), TiO2 and BaTiO3 are very promising candidates for applications with exhibiting higher dielectric constant, high refractive index and high chemical stability. The growth of TiO2 and BaTiO3 thin films on various substrates i.e. (100) silicon、(100) GaAs、(100) InP and (100) MgO are studied by MOCVD using Ti(i-OC3H7)4, Ba(DPM)2, N2O and O2 as precursors. The growth was performed in a cold wall horizontal system in the temperature range of 280~750℃. The growth rates and structure of TiO2 and BaTiO3 films are affected by the substrate temperature and reactor pressure, etc. The phase transition properties of TiO2 were studied via X-ray diffraction measurements. X-ray diffraction examination shows that phase transition of TiO2 films are at the same temperature of 450 oC on different substrates. Phase-pure rutile is obtained down to 450℃ on InP (100) and GaAs (100), while phase-pure anatase is obtained up to 450℃on MgO (100). The optical and electrical properties are associated with the film structures. TiO2 single phase films with rutile (110) orientation were successfully grown on InP (100) at 500℃. In-plane epitaxial relationship of anatase TiO2 (100) // MgO (100) is present between 300℃ and 375℃. In addition, the influences of substrate temperature and oxidizer on the structural and electrical properties of BaTiO3 films will be also studied. However, TiO2 and BaTiO3 films have columnar structures acted the paths of leakage current resulting low dielectric constant. We use thermal annealing to improve the quality of TiO2 with respect to leakage current density and dielectric constant. Dielectric constants of annealed TiO2 films were as high as 110.08. Leakage current density reduced to 5 × 10-5 A/cm2. In the future, to improve the crystal structure of the films is the goal in our study.

Acknowledgment................................................................3
List of figures..............................................................12
List of tables...............................................................17
Abstract.....................................................................18
1.Introduction...............................................................20
1-1 Developments in DRAM.....................................................20
1-2 Promising candidates of high dielectric constant materials for high-density DRAM.........................................................................21
1-3 Comparison of deposition methods of BaTiO3...............................23
1-4 Advantages of MOCVD......................................................24
2.Experiments................................................................26
2-1 Growth system of MOCVD...................................................26
2-2 Properties of metalorganic precursors....................................27
2-2-1 Ti metalorganic precursor..............................................27
2-2-2 Ba metalorganic precursor..............................................28
2-3 Growth procedures........................................................28
2-3-1 Si wafer cleaning procedures...........................................28
2-3-2 GaAs wafer cleaning procedures.........................................29
2-3-3 InP wafer cleaning procedures..........................................30
2-3-4 MgO wafer cleaning procedures..........................................30
2-3-5 Preparations of TiO2 and BaTiO3 thin films.............................31
2-4 Characterizations........................................................31
2-4-1 Physical properties....................................................31
2-4-2 Chemical properties....................................................32
2-4-3 Electrical properties..................................................32
3.Results and Discussion.....................................................34
3-1 Structural and electrical properties of TiO2 on GaAs.....................34
3-1-1 Thickness and growth rate of TiO2 on GaAs as a function of substrate temperature..................................................................34
3-1-2 Refractive index of TiO2 on GaAs as a function of substrate temperature..................................................................36
3-1-3 X-ray diffraction patterns of TiO2 on GaAs as a function of substrate temperature..................................................................36
3-1-4 Chemical analyses of TiO2 on GaAs as a function of substrate temperature..................................................................37
3-1-5 Surface morphologies of TiO2 on GaAs as a function of substrate temperature..................................................................37
3-1-6 Dielectric constant and leakage current density of TiO2 on GaAs as a function of substrate temperature............................................38
3-2 Structural and electrical properties of TiO2 on InP......................39
3-2-1 Thickness and growth rate of TiO2 on InP as a function of substrate temperature..................................................................39
3-2-2 Refractive index of TiO2 on InP as a function of substrate temperature..................................................................40
3-2-3 X-ray diffraction patterns of TiO2 on InP as a function of substrate temperature..................................................................40
3-2-4 Chemical analyses of TiO2 on InP as a function of substrate temperature..................................................................42
3-2-5 Surface morphologies of TiO2 on InP as a function of substrate temperature..................................................................42
3-2-6 Leakage current density of TiO2 on InP as a function of substrate temperature..................................................................43
3-3 Structural and electrical properties of TiO2 on MgO......................44
3-3-1 Thickness and growth rate of TiO2 on MgO as a function of substrate temperature..................................................................44
3-3-2 Refractive index of TiO2 on MgO as a function of substrate temperature..................................................................46
3-3-3 X-ray diffraction patterns of TiO2 on MgO as a function of substrate temperature..................................................................46
3-3-4 Chemical analyses of TiO2 on MgO as a function of substrate temperature..................................................................47
3-3-5 Surface morphologies of TiO2 on MgO as a function of substrate temperature..................................................................48
3-3-6 Dielectric constant and leakage current density of TiO2 on MgO as a function of substrate temperature............................................49
3-4 Effects of heat treatments on TiO2 thin films............................50
3-4-1 Structural and electrical properties of TiO2 thin films under different heat treatments..............................................................50
3-4-2 X-ray diffraction patterns of TiO2 thin films under different heat treatments...................................................................53
3-4-3 Chemical analyses of TiO2 thin films under different heat treatments...................................................................54
3-4-4 Surface morphologies of TiO2 thin films under different heat treatments...................................................................55
3-5 Structural and electrical properties of BaTiO3 on Si in O2...............56
3-5-1 Thickness and growth rate of BaTiO3 on Si in O2 as a function of substrate temperature........................................................56
3-5-2 X-ray diffraction patterns of BaTiO3 on Si in O2 as a function of substrate temperature........................................................57
3-5-3 Chemical analyses of MoO3..............................................58
3-5-4 Surface morphologies of BaTiO3 on Si in O2 as a function of substrate temperature..................................................................58
3-5-5 Dielectric constant and leakage current density of BaTiO3 on Si in O2 as a function of substrate temperature..........................................59
3-6 Structural and electrical properties of BaTiO3 on Si in N2O..............58
3-6-1 Thickness and growth rate of BaTiO3 on Si in N2O as a function of substrate temperature........................................................60
3-6-2 Refractive index of BaTiO3 on Si in N2O as a function of substrate temperature..................................................................61
3-6-3 Surface morphologies of BaTiO3 on Si in N2O as a function of substrate temperature..................................................................61
3-6-4 X-ray diffraction patterns of BaTiO3 on Si in N2O as a function of substrate temperature........................................................62
3-6-5 Dielectric constant and leakage current density of BaTiO3 on Si in N2O as a function of substrate temperature..........................................63
3-7 Structural and electrical properties of BaTiO3 on MgO....................64
3-7-1 Thickness and growth rate of BaTiO3 on MgO as a function of substrate temperature..................................................................64
3-7-2 Refractive index of BaTiO3 on MgO in N2O as a function of substrate temperature..................................................................65
3-7-3 Surface morphologies of BaTiO3 on MgO in N2O as a function of substrate temperature..................................................................65
3-7-4 X-ray diffraction patterns of BaTiO3 on MgO in N2O as a function of substrate temperature........................................................66
4.Conclusions................................................................67
References..................................................................116

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