隨著社群網路、物聯網、人工智能等應用逐漸普及，未來巨量數據將不斷產生，因此記憶體儲存的需求將會大幅攀升，高效且節能的次世代非揮發性記憶體技術發展勢在必行。其中，次世代非揮發性記憶體以電阻式記憶體(RRAM)最具潛力，目前電阻式記憶體的轉態物理機制仍有許多爭論尚待解決，釐清這些問題便能加速推動其商業化。
本論文研究針對氧化物電阻式記憶體元件的電阻切換機制與氧離子在其中的作用提出一完整論述與模型解釋。在物理機制的研究當中，專注於現象觀察並設計材料及元件結構進行電性分析，經由分析結果對氧化物電阻式記憶元件進行深入的研究與探討。若操作鋅(Zn)電極的氧化物電阻式記憶元件會發出氧電漿發光光譜；以紫外光照射使用透明電極的電阻式記憶元件結構(ITO/ZnO/TiN)並進行操作，氧化鋅會吸收紫外光使氧離子被活化，而氧離子會在電壓驅動下改變元件的電流傳導機制，證實電阻式記憶元件的切換特性與氧離子具有強烈的關係。
將銦錫氧化物(ITO)材料中間嵌入一層極薄的二氧化矽元件結構(ITO/SiO2/ITO/TiN)，可使氧離子能夠通過電壓操作流動於電極與絕緣層之間，產生氧濃度梯度，因此能以極低的電壓操作元件。另外，將二氧化矽(SiO2)嵌入氧化鋅絕緣層中間的結構(Pt/ZnO/SiO2/ZnO/TiN)，由於二氧化矽層相對介電常數較低，電場集中於氧化矽層，會形成大量氧空缺而成為氧離子儲存區域，這個儲存氧離子的區域則成為電阻式記憶元件的阻絲切換區域，使其可在單一電阻式記憶元件內形成互補式電阻記憶元件的切換特性。
根據材料相對介電常數對電阻式記憶元件結構的影響，進行COMSOL電場模擬，透過相對介電常數較高的側壁材料氧化鉿(HfO2)，有效抑制電場往側壁逸散，在元件尺寸縮小時使絕緣切換層的成形電壓能保持穩定，並且能夠維持元件的可靠度。
除此之外，我們開發出一種先進的電子元件處理技術，超臨界流體氮化處理技術，本技術能在室溫狀態有效將氨分子藉由超臨界二氧化碳帶入各種電子元件中反應，能夠改變材料性質並有效提升電阻式記憶元件的性能與可靠度，此革命性技術未來將可用於提升各種電子元件性能。

With popular applications in social networking, the Internet of things (IoT), and artificial intelligence (AI), a large amount of data processing will be continuously required. Thus, the need for data storage will also rise sharply in the near future. Implementing highly efficient and energy-saving next-generation non-volatile memory will become an imperative. Among many possible candidates, the one with the most potential is resistance random access memory (RRAM). However, the conducting mechanism of RRAM is still a topic of debate. Clarifying this issue in RRAM will be beneficial to its commercialization in real applications.
In this study, the resistive switching mechanism of oxide-based RRAM and the role of oxygen ions are thoroughly investigated in order to propose a complete model explanation. To research the physical mechanism, we focus on observations of the electrical measurement to further modify the material combinations and device structure. When zinc (Zn) was applied as the electrode in the oxide-based RRAM, an oxygen plasma emission spectrum was observed in the memory device. In addition, we discuss a RRAM device with ITO/ZnO/TiN structure under ultraviolet light illumination to activate oxygen ions, and thus, to modify the current transport mechanisms. This is because the absorption of ultraviolet by the ZnO layer drives the generated oxygen ions when operating the RRAM device. These results confirm that the switching characteristics of RRAM are strongly related to the oxygen ions.
Indium tin oxide (ITO)-based RRAM with an inserted SiO2 thin film as ITO/SiO2/ITO/TiN was proposed to obtain ultra-low operating voltages. Because of the effect of oxygen concentration gradient induced by the inserted SiO2 and ITO electrode in this ITO-based RRAM device, the oxygen ions can be driven with an ultra-low operating voltage. Further, we utilized a SiO2 layer inserted into the resistive switching layer as the Pt/ZnO/SiO2/ZnO/TiN structure to realize complementary resistive switching (CRS) characteristics in a single cell device. Owing to the intrinsic electrical properties of the low k material, we could modify the degree of SiO2 film breakdown and the oxygen ion storage capacity.
A novel high-permittivity (high-k) material of hafnium oxide (HfO2) serving as side-wall spacer in the RRAM has been realized to solve the critical upward tendency in forming voltage during device scale-down. The simulated electrical field results from COMSOL software suggest the RRAM device with a high-k spacer can effectively confine the electric field within the insulator layer during forming process. Introducing the high-k spacer in the RRAM can successfully eliminate the rise in forming voltage at small device size without affecting device reliabilities such as endurance and retention.
Finally, an advanced electron device treatment technology was developed. The supercritical fluid (SCF) nitridation treatment can further enhance device performance and reliability in RRAM. This SCF treatment can effectively introduce ammonia molecules into numerous electron devices at room temperature by the CO2 SCF. This revolutionary technology can be applied to various electron devices to improve their performance.

Contents
Acknowledgment………………………..……….…………….………………………………..…...............................................................................................................i
Chinese Abstract …..………………..………………………...…………………………………….........................................................................................................…ii
English Abstract….…………………..………………………...…………………………………...............................................................................................................iii
Contents……………..……..………………………...…………………………………..........................................................................................................................…v
Figure Captions……………..……..………………………...………………………………….................................................................................................................vii
Table Captions……………..……..………………………...…………………………………...................................................................................................................xii
Chapter 1 Background Introduction ………………………………………………………………............................................................................................................1
1-1 Introduction of memory ………………………………………………..………………………..........................................................................................................1
1-2 The Emerging Memory………………………………………………..……………………......................................................................................................….….4
Chapter 2 Introduction of RRAM..……………………………………....………...……….....................................................................................................................12
2-1 Basic Introduction of RRAM…………………………………………………………………...........................................................................................................12
2-2 The materials of RRAM………………………………………………………………………...........................................................................................................13
2-3 Switching Mechanism of RRAM……………………………………….………………….....................................................................................................……...19
2-4 Carrier Conduction Mechanisms in RRAM………………………………….….…………............................................................................................................27
2-5 Commercial Application of RRAM……………………………….….………………….....................................................................................................…….….31
2-6 RRAM's Global Development and Challenges…………………………….….……….....................................................................................................……....35
2-7 Motivation of this Dissertation…………………………….….………………………….....................................................................................................…….....41
Chapter 3 Resistive Switching Modification by Ultraviolet Illumination in Transparent Electrode Resistive Random Access Memory……………………………....45
3-1 Motivation………………………………………………………………………………………..........................................................................................................45
3-2 Experimental………………………………………………………………......................................................................................................................................45
3-3 Results and Discussion……………………………………………….………………….....................................................................................................…….…46
3-4 Summary…………………………………….…………………………..………………….....................................................................................................……...50
Chapter 4 Ultra-low Switching Voltage Characteristic induced by Inserting SiO2 layer on ITO-base Resistance Random Access Memory……...……………......51
4-1 Motivation…………………………………………………………………………………….......................................................................................................…...51
4-2 Experimental……………………………………………………………...………………….....................................................................................................….....52
4-3 Results and Discussion……………………………..………………..………………………......................................................................................................….54
4-4 Summary………………………………………………………………………………………...........................................................................................................57
Chapter 5 Complementary Resistive Switching Behavior Induced by Varying Forming Current Compliance in Resistance Random Access Memory……….................................................................................................................................................................................................................................59
5-1 Motivation…………………………………………………………….…….....................................................................................................................................59
5-2 Experimental………………………………………………………….….…………………….....................................................................................................….60
5-3 Results and Discussion……………………………………….……………………………….........................................................................................................62
5-4 Summary……………………………………………………………………………………….....................................................................................................…..65
Chapter 6 Solving the Scaling Issue of Increasing Forming Voltage in Resistive Random Access Memory Using High-k Spacer Structure….............................66
6-1 Motivation…………………………………………………………….………………………............................................................................................................66
6-2 Experimental……………………………………………………………………………..…......................................................................................................…....67
6-3 Results and Discussion……………………………………….…………………………….....................................................................................................…....69
6-4 Summary……………………………………………………………………………………........................................................................................................…..76
Chapter 7 Novel Device Treatment Process Technology: Supercritical Fluids Nitridation………………………………………………………………………………...77
7-1 Introduction……………………………………………………………………………….......................................................................................................……....77
7-2 Experimental………………………………………………………………………….….….....................................................................................................……..81
7-3 Results and Discussion……………………………………….………………………….....................................................................................................……....85
7-4 Summary…………………………………………………………………….………….....................................................................................................………….88

Conclusion…………………………………………………………..…………………………….....................................................................................................…......89
References…………………………………………………………..…………………………….....................................................................................................……..90
Publication List……………………………………………………………………………………….....................................................................................................…..96

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