當元件尺寸不斷地縮小，採用高介電係數材料取代傳統的二氧化矽已是刻不容緩的事。而二氧化鈦由於具有高介電常數、高折射率、高化學穩定性，故適合應用在動態記憶體中電容的介電材料。
我們採用水平、低壓、冷壁式之有機金屬化學氣相沈積法來成長二氧化鈦薄膜，採用的原料為Ti(i-OC3H7)4，並以N2O作為氧化氣體。成長溫度從400℃到650℃。由X光繞射的結果得知二氧化鈦薄膜為多晶結構且銳鈦礦相與金紅石相共存的溫度約為650℃。而成長溫度明顯地影響二氧化鈦薄膜的電性，在經由熱退火處理後電性也有顯著的改善。我們發現在650℃成長的二氧化鈦薄膜，經由在O2中750℃的熱退火處理20分後具有最高的介電常數為100.3,而在550℃成長的二氧化鈦薄膜，經由在O2中750℃的熱退火處理20分後則具有最小的漏電流。此外，我們將二氧化矽薄膜利用液相沈積法成長在有機金屬化學氣相沈積二氧化鈦薄膜上，發現此方法可以有效地降低漏電流並保有高的介電係數。

As the electronic device scale down, replacing conventional SiO2 with high dielectric constant material is very important. Due to its have high dielectric constant (ε// = 170, ε⊥ = 90), high refractive index (~2.5) and high chemical stability. TiO2 is a promising candidate for fabricating thin dielectrics in dynamic random access memory (DRAM) storage capacitors and as gate dielectrics of metal-oxide-semiconductor field effect transistor (MOSFET) without the problem of conventional SiO2 thickness scaling down in ULSI processes because of its high dielectric constant.
TiO2 thin films deposited on p-type (100) Si substrate were investigated by a cold wall horizontal MOCVD system using Ti(i-OC3H7)4, N2O as precursors in the deposition temperature range from 400 ℃ to 650 ℃.
XRD results indicate that the structures of TiO2 films are polycrystalline and mixture of anatase and rutile phases coexist in the film at the deposition temperature of 650 ℃. Electrical properties are strongly influenced by deposition temperature. The electrical properties of as-deposited TiO2 films can be improved by annealing treatment. The TiO2 film at the deposition temperature of 650 ℃ has the highest dielectric constant of 100.3 and at the deposition temperature of 550 oC has the lowest leakage current density of 2.07×10-7 A/cm2 under the applied electric field of 5 MV/cm after annealing for 20 minutes at 750 ℃ in O2 ambient.
In order to obtain the better electrical properties of TiO2 films on Si substrate, LPD-SiO2 thin films were deposited on the polycrystalline MOCVD-TiO2 films. The minimum equivalent oxide thickness of LPD-SiO2/post-annealed TiO2 film is 51.13

1.Introduction......................1
1-1 Developments in DRAM............1
1-2 Properties of TiO2............. .2
1-3 Comparison of deposition methods of TiO2 .....4
1-4 Advantages of MOCVD..............4
1-5 Experiment Motivation of LPD-SiO2/MOCVD-TiO2/Si
structure...................... 5
2.Experiments.......................7
2-1 CVD theorem...................7
2-2 Deposition system of MOCVD..... 8
2-3 Properties of metalorganic precursors.........9
2-3-1 Ti metalorganic precursor...................9
2-3-2 N2O decomposed..............................9
2-4 Deposition procedures.........................10
2-4-1 Si wafer cleaning procedures................10
2-4-2 Aluminum metal wafer cleaning processes.....11
2-4-3 Preparations of TiO2 films..................11
2-5 Characterization..............................11
2-5-1 Physical properties.........................11
2-5-2 Chemical properties.........................12
2-5-3 Electrical properties.......................13
3.Results and Discussion..........................18
3-1 Dependence of properties on deposition
temperature...................................18
3-1.1 Thickness and growth rate as a function of
deposition temperature......................18
3-1.2 XRD patterns as a function of deposition
temperature.................................19
3-1.3 SEM morphologies as a function of deposition
temperature.................................20
3-1.4 AFM surface roughness of TiO2 films as a function of
deposition temperature......................20
3-1.5 SIMS depth profile of TiO2 films as a function of
deposition temperature......................21
3-1.6 ESCA analyses of TiO2 films as a function of
deposition temperature......................22
3-1.7 Dependence electrical properties of TiO2 films on
deposition temperature......................24
3-1.7.1 Leakage current density as a function of
deposition temperature......................24
3-1.7.2 C-V characteristics and dielectric constant of
TiO2 films as a function of
depositiontemperature.....................25
3-2 Improvement in electrical properties of as- deposited
TiO2 films by annealing treatment.............28
3-2.1 ESCA analyses of post-annealed TiO2 films of as a
function of deposition temperature..........29
3-2.2 Investigation of electrical properties of as-
deposited TiO2 by annealing treatment.......30
3-3 LPD-SiO2/ MOCVD-TiO2 /Si structure............32
3-3.1 SIMS depth profile of LPD-SiO2/MOCVD-TiO2/Si
structure...................................34
3-3.2 FTIR of LPD-SiO2/ MOCVD-TiO2 film...........34
3-3.3 Electrical properties of LPD-SiO2/ MOCVD-TiO2/Si
structure...................................34
4.Conclusions.....................................37
REFERENCES........................................39
FIGURES...........................................47~104
TABLES............................................105~109

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