臺灣博碩士論文加值系統

本篇論文探討應用於動態隨機存取記憶體 (DRAM) 之鈦酸鍶鋇高介電薄膜層的製程與特性 。 除了鈦酸鍶鋇薄膜本身優異的電性外 ， 製程條件改善更有助於製備高品質薄膜 ， 符合新一代記憶體要求 。 因此 , 我們以液態霧化源沉積系統製備鈦酸鍶鋇薄膜 , 再施以常壓快速熱退火處理和低壓快速熱退火處理來增進薄膜的結晶性使薄膜呈現出最優異的電性表現。
根據實驗結果 , 薄膜經過傳統的長時間緩慢爐冷熱退火處理後 , 改善了結晶性但漏電流也跟著變大 ； 相反的 ， 快速熱退火處理卻能以瞬間高能量促使薄膜緻密性結晶 , 降低漏電流 。 此外 , 我們也量測了變化溫度下的電流對電場關係以討論不同製程條件和厚度的薄膜漏電流機制 , 以期了解薄膜厚度與薄膜結構與電性相互關係。
最後 , 以電漿退火處理改善鈦酸鍶鋇薄膜特性 ， 並分析探討電漿退火處理對薄膜物性和電性的影響 , 提供可能應用上之參考 。

BaxSr1-xTiO3 thin films are highly promising storage dielectrics in DRAM applications because of their excellent electrical properties . In this thesis , we used the liquid source misted chemical deposition method (LSMCD) to deposit high quality BST thin films . The rapid thermal annealing (RTA) and low pressure — rapid thermal annealing(LP-RTA) are carried out to enhance the film crystallinity and improve the properties of BST thin films for DRAM capacitor application.
On the basis of experimental results, the RTA can achieve the good film crystallinity with low leakage current because the rapid impulsive heat energy make the grains smaller but denser compared with the conventional furnace annealing, which leads to larger grain size and higher leakage current. In addition, we measured and plotted the relation of leakage current v.s. electric field at various temperature for investigating the conduction mechanisms of the films in different processing conditions and thicknesses.
Finally, the effect of plasma annealing on the electrical properties of the films was also investigated in order to provide useful information for possible applications.

CONTENTS
ABSTRACT(CHINESE)…………………………………………………………….i
ABSTRACT(ENGLISH)…………………………………………………………….ii
ACKNOWLEDGEMENTS………………………………………………………...iii
CONTENTS………………………………………………………………………...iv
TABLE LISTS………………………………………………………………………vii
FIGURE CAPTIONS……………………………………………………...………viii
CHAPTER 1 Introduction…………………………………………………………1
1-1 DRAM application………………………………………………………..……..1
1-2 BST structure…………………………………………………………………....3
1-3 Deposition method ……………………………………...………………………4
CHATPER 2 Experimental Details………………………………………………..8
2-1 Film fabrication……………………………………………....………………...8
2-2 Preparation of BST thin films……..……………………………………………9
2-3 Rapid thermal annealing system…………………………..…….………………9
2-4 Physical measurements…………..…………………………………………….10
2-4-1 X-Ray diffraction analysis (XRD)………………………………………10
2-4-2 Atomic force microscopy (AFM)……………………………………….10
2-4-3 Scanning electron microscopy (SEM)………………….…………...…...11
2-4-4 Current-Voltage(I-V) measurements...…………………………………..11
2-4-5 Capacitance-Voltage(C-V) measurements………………………………11
CHAPTER 3 Results and Discussion……………………………………...…….13
3-1 Properties of rapid thermal annealing BST thin films …....…………………...13
3-1-1 Properties of rapid thermal annealing (RTA)BST thin films prepared at high pressure (760torr) ………………………...……………………….13
3-1-1-1 Motivation………………………………………………………..13
3-1-1-2 Sample preparation………………………………………………15
3-1-1-3 Electrical measurements.………………………………………...15
3-1-2 Properties of BST thin films with low pressure(50torr) rapid thermal
annealing (LP-RTA)……………………………………………………..19
3-1-2-1 Motivation……………………………………………………….19
3-1-2-2 Sample preparation……………………………………………...20
3-1-2-3 Electrical measurements.…………………………………….….21
3-1-3 Conduction mechanism…..……………………………………………...25
3-1-3-1 Conduction mechanism in films of different thickness………....25
3-1-3-2 Conduction mechanism between RTP and LP-RTP……...….…31
3-1-3-3 TDDB reliability…………………………………………….….34
3-1-4 Comparison of physical properties………………………………………35
3-1-4-1 X-Ray diffraction analysis (XRD)……….……………………..35
3-1-4-2 Scanning electron microscopy (SEM)…....…………………….35
3-1-4-3 Atomic force microscopic (AFM)……….……………………..36
3-1-4-4 Secondary ion mass spectrometry (SIMS).……………………..37
3-1-5 Summary…………………………………………………………………38
3-2 The plasma effect on BST thin film……………………………………………39
3-2-1 Motivation ………………………………………………………………39
3-2-2 Sample preparation………………………………………………………39
3-2-3 Electrical measurements…………………………………………………40
3-2-3-1 Annealing-plasma sequence…...………………………………….40
3-2-3-2 Plasma-annealing sequence……………………………………….42
3-2-4 Physical measurements…………...……………………………………..43
3-2-4-1 Annealing-plasma sequence……..……………………………….43
3-2-4-2 Plasma-annealing sequence……………………………………….44
3-2-5 Summary...………………………………………………………………44
3-3 Effect of plasma on BST thin film with interfacial oxide layer on Pt bottom electrode……………………………………………………………………...…44
3-3-1 Motivation……………………………………………………………….45
3-3-2 Sample preparation………………………………………………………46
3-3-3 Electrical measurements…………………………………………………46
3-3-4 Physical measurements………………………………………………….47
3-3-5 Summary………………………………………………………………...48
CHAPTER 4 Conclusions………………………………………………………..50
REFERENCES..…………………………………………………………………….52

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