1 research outputs found
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Όλ¬Έμμ μ μν ꡬ쑰μ μ λ° λΆμμ κ΄ν μ°κ΅¬λ μλ‘μ΄ μ ν λ©λͺ¨λ¦¬μ μ μ λ ₯ κ³ μ§μ νμ μμ΄ μ΄μ κ°λ₯μ±μ λ³΄λ€ μ€μ¦μ μΌλ‘ μμΈ‘ν μ μλ ν λλ₯Ό λ§λ ¨ν΄μ£Όλ©°, κ·Όλ λ° κ°κΉμ΄ λ―Έλμ κ°λ°λ μ νλ©λͺ¨λ¦¬μ μ μ λ ₯νλ₯Ό ν΅ν ν¨κ³Όμ μΈ μμ°νμ μμ΄, ν¨κ³Όμ μΈ λ°©ν₯μ μ μν μ μλ λ°©λ²κ³Ό ν λμ κ·Όκ±°ν μ°κ΅¬ κ²°κ³Όλ₯Ό μ μνλ€.Over the recent years, rapid progress of information technology (IT) has enabled many researchers to focus on developing the new memories. Compared to other conventional memories such as dynamic random access memory (DRAM) and flash memory, new memory has numerous advantages such as low writing power, fast access time, and superb scalability. In particular, the development of resistive random access memory (RRAM), which is a low cost memory using resistance difference depending on the applied electrical signals, may enable the massive production due to its great compatibility with the complementary metal oxide semiconductor (CMOS) process.
However, even though RRAM is very promising in many respects as described above, some shortcomings such as limited understanding of switching mechanism and relatively high switching current still need to be improved. In addition, in unipolar resistive switching, it is very difficult to implement high-density RRAM with conventional metal-insulator-metal (MIM) structure due to large reset/set distribution, large access device related with current compliance, and relatively high power consumption.
To solve these problems in RRAM research, a few breakthroughs based on the correct understandings of resistive switching mechanism should occur. In these respects, the relations of analytical resistive switching parameters and switching characteristics, which are very important factors for understanding conductive filament (CF) in unipolar RRAM cell, are investigated. In addition, the effects of CF modulation at the switching interface and its area- and structure-related switching characteristics are also discussed.
Particularly in this thesis, the evidence of switching area scaling effect on reset current (IRESET) reduction in unipolar RRAM is investigated. Especially, a novel metal-insulator-metal (MIM) structure designed for low-power RRAM application (called crown shape RRAM structure) is proposed to elucidate the area effect for the first time. We demonstrate that the control of contact size and deposition orientation of resistive material is useful in improving the initial CF formation in a crown shape cell. Simple fabrication flow and device performances are also evaluated in terms of forming-less process. Numerical simulation is also performed using 3D random circuit breaker model (RCB) to verify the proposed structure.
In the end, IRESET reduction is finally confirmed by using highly scaled hole contact cell structure. We fabricated this scaled hole contact cell, which makes it possible to reduce the total area of CF (ACF) by reducing the switching area. It is verified that the decrease of CF area in the critical switching region contributes to IRESET reduction. It is clear that the effect of switching area reduction is significant. Various evidances of ACF modulation such as increase in on-state resistance (RON) and reset voltage (VRESET), decrease in IRESET and switching power are investigated. Elimination of unwanted leakage current in a scaled contact hole structure is realized by adopting a double-deposited inter layer dielectric (ILD) mold process. These results strongly support the scaling approach, which contributes to the IRESET reduction in low-power unipolar RRAM application.Abstract i
Chapter 1
Introduction
1.1 Overview of RRAM 1
Chapter 2
Unipolar Resistive Switching
2.1 Conductive Filament (CF) in Initial Resistive Cell States 14
2.2 CF Control in Switching Interface in Single Layer Cell 19
2.3 CF Control in Switching Interface in Bi-layer Cell 32
2.3.1 Bi-layer cell with conductive defect effect 32
2.3.2 Bi-layer cell with thickness effect 38
2.3.3 Experimental results: Al inserted bi-layer structure 44
2.3.4 Experimental results: statistical analysis 50
2.4 Reset Current Reduction and CF Modulation 56
2.5 Summary 61
Chapter 3
Scaling Feasibility in Crown Shape RRAM
3.1 Introduction 63
3.2 Experimental Results 65
3.3 Summary 91
Chapter 4
Scaling Characterisitics in Trench Contact RRAM
4.1 Introduction 93
4.2 Experimental Results 95
4.3 Summary 119
Chapter 5
Conclusion 121
Bibliography 123
Abstract in Korean 134Docto