臺灣博碩士論文加值系統

近年來，由於非揮發性記憶體的應用與發展受到矚目，加上快閃記憶體微縮極限，所以新世代非揮發性記憶體的研究正緊鑼密鼓地展開。其中，電阻式非揮發性記憶元件具有高密度、高操作速度、低功率消耗、高耐久性、微縮能力高及非破壞性資料讀取等優點，使其成為新世代非揮發性記憶元件的熱門人選。
在本篇論文中，提出電阻轉換特性的物理模型與理論基礎在氮化鈦/二氧化矽/鐵白金的結構上，且與氧空缺和相變化有關。其內容可分為三大部份，包含利用結構上的不同，亦或不同熱處理的方式與小尺寸元件效應，來驗證論文中所提到的物理模型與電性特性的研究。在利用不同結構來檢視記憶體特性部份，置換不同上下電極材料與二氧化矽厚度，來檢視電阻有效轉態區的位置。其結果驗證有效轉態區位置在鐵白金底電極與二氧化矽的界面上，且和Fe元素有一定的相關性。在利用不同的熱處理方式來檢視電阻轉態特性部分，驗證了氧化鐵與氧空缺量的多寡程度亦會影響到轉態週期與電流特性。最後，製作小尺寸元件來檢視轉態特性，發現實驗結果與電性水管理論的結果相似，並且可從電性結果更加驗證物理模型的確立。最後提出電性水管的基本物理與數學模型，做為未來可能再增進的研究方向。

Recently, since nonvolatile memories acquire a lot of attention and flash memories are facing with the scale limit issue, the next generation nonvolatile memory has been carried out to discover extensively. The resistive random access memories (ReRAMs) that have the strengths of high cell density array, high operation speed, low power consumption, high endurance, lower scale limit and non-destructive readout, are one of the most potential candidate for flash memories.
In this thesis, a physical model and mechanism which is about the role of oxygen vacancies and phase change in TiN/SiO2/PtFe resistance nonvolatile random access memories is proposed. This study can be categorized into three parts, different structures, different thermal treatments and small size devices, all of these electrical results can support the model and mechanism. In the first part, replacing metal electrode materials and SiO2 thickness with different structures was found the results which the effective resistance switching region is at interface region, and Fe element plays an important role to cause resistance switching behavior. In the second part, with different thermal treatments to examine the resistance switching characteristics, was discovered that amount of Fe2O3 and oxygen vacancies would affect endurance reliability and electric characteristics. In the third part, using small size cells to examine the resistance switching characteristics was found the results which are similar with the electric faucet theory and the proposed model. Moreover, a possible model about electric faucet is proposed by physical and mathematical methods. Further investigation, including interfacial electric faucet structure and electrode effects, would help to achieve a better understanding.

CHINESE ABSTRACT I
ABSTRACT II
ACKNOWLEDGEMENT IV
CONTENTS V
TABLE CAPTIONS IX
FIGURE CAPTIONS X
CHAPTER 1 INTRODUCTION
1.1 INTRODUCTION TO NON-VOLATILE MEMORY 1
1.1.1 Flash 2
1.1.2 Resistive random access memory (ReRAM) 2
1.1.3 Structure and fabrication 3
1.1.4 Material classification 4
1.1.5 Operation and circuit realization 4
1.2 CONDUCTING MECHANISMS IN OXIDES [25] 6
1.2.1 Ohmic conduction 6
1.2.2 Space charge limited current 7
1.2.3 Schottky emission 8
1.2.4 Frenkel-Poole emission 8
1.2.5 Tunneling 9
1.3 MODELS OF RESISTIVE SWITCHING MECHANISMS 9
1.3.1 Filament-type resistive switching [23] 10
1.3.2 Interface-type resistance switching [23] 10
CHAPTER 2 EXPERIMENT DETAILS 16
2.1 MOTIVATION 16
2.2 SAMPLE FABRICATION 16
2.2.1 Standard RCA clean 17
2.2.2 Growth of buffer SiO2 18
2.2.3 Deposition of bottom electrode 18
2.2.4 Preparation of insulator SiO2 19
2.2.5 Deposition of top electrodes 19
2.2.6 Deposition of passivation oxide 20
2.2.7 Deposition of probing electrodes 20
2.3 ANALYSES AND MEASUREMENTS 20
2.3.1 Inductively coupled plasma-mass spectrometry (ICP-MS) 21
2.3.2 X-ray diffraction (XRD) 21
2.3.3 X-ray photoelectron spectrometer (XPS) 21
2.3.4 Auger electron spectroscopy (AES) 21
2.3.5 Secondary ion mass spectroscopy (SIMS) 22
2.3.6 Electrical measurements 22
2.3.6.1 Bistable resistive switching 23
2.3.6.2 Endurance 23
2.3.6.3 Retention 23
CHAPTER 3 RESULTS AND DISCUSSIONS 26
3.1 DEVICE STRUCTURES AND CHARACTERISTICS 26
3.1.1 Various bottom electrode metals 26
3.1.1.1 Mechanism of Forming Process 27
3.1.1.2 Mechanism of Phase Change in the Reset Process 28
3.1.1.3 Mechanism of Oxygen Vacancies in the Reset Process 28
3.1.1.4 Band diagram in the Reset Process 29
3.1.1.5 Mechanism of Phase Change in the Set Process 29
3.1.1.6 Mechanism of Oxygen Vacancies in the Set Process 30
3.1.1.7 Band diagram in the Set Process 31
3.1.2 Effects of Top Electrode Metal Effects 31
3.1.3 Effects of SiO2 Thicknesses 32
3.1.4 Summary I 32
3.2 EFFECTS OF BOTTOM ELECTRODE METALS 33
3.2.1 Electrical properties 33
3.2.1.1 Bistable Resistance switching 33
3.2.1.2 Current-Voltage Fitting 34
3.2.1.3 I-V Characteristics Distribution 34
3.2.2 Summary II 35
3.3 THERMAL TREATMENT EFFECTS 35
3.3.1 Electrical Characteristics 36
3.3.1.1 Bistable resistance switching and Endurance 36
3.3.2 Material analysis 37
3.3.2.1 SIMS 37
3.3.2.2 XPS 37
3.3.2.3 XRD 38
3.3.3 Comprehensive Comparison 38
3.3.3.1 Endurance Reliability 38
3.3.3.2 The Low Resistance State 39
3.3.3.3 The High Resistance State 40
3.3.4 Summary III 40
3.4 SMALL SIZE EFFECTS 41
3.4.1 Experimental 41
3.4.2 Bistable Resistance Switching 41
3.4.3 Material Analysis 42
3.4.4 Current Fitting 42
3.4.5 Size Effects 43
3.4.6 Set Process with Different Sizes 44
3.4.7 Reset Process with Different Sizes 44
3.4.8 Compliance Current and Switching Process 45
3.4.8.1 Physical Model of Electric Faucet 45
3.4.8.2 Mathematical Model of Electric Faucet 47
3.4.9 Summary 48
CHAPTER 4 CONCLUSION 83
REFERENCE 84

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