過渡-稀土基垂直式磁性穿隧接合之製備與探討

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研究生：	徐柏清 Po-Ching Hsu
論文名稱：	過渡-稀土基垂直式磁性穿隧接合之製備與探討 Fabrication and Investigation of RE-TM-based Perpendicular Magnetic Tunnel Junction
指導教授：	賴志煌 Chih-Huang Lai
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 材料科學工程學系 Materials Science and Engineering
論文出版年：	2006
畢業學年度：	94
語文別：	英文
論文頁數：	75
中文關鍵詞：	過渡-稀土、磁性穿隧元件、垂直異向性、氧化鋁、磁性隨機記憶體、熱輔助寫入、垂直、穿隧磁阻效應
外文關鍵詞：	Rare Earth-Transition Metal, magnetic tunnel junction, perpendicular anisotropy, aluminum oxide, Magnetic Random Access Memory, thermally-assisted writing, perpendicular, Tunneling Magnetoresistance (TMR)
相關次數：	點閱：2 下載：0
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摘要
此實驗中，我們使用RE-TM材料製備具有垂直磁矩的磁性穿隧元件。此RE-TM基垂直式磁性穿隧元件可以減小自由層中漩渦結構的發生。因此，此垂直穿隧元件可以進一步地縮小化以符合高密度磁性隨機存取記憶體的要求。
實驗程序如下:首先我們建立完整的垂直式磁性穿隧元件製作程序，包括最佳化傳統水平式磁性穿隧元件AlOX穿隧絕緣層的製程參數，並且製作垂直式磁性穿隧元件完整的模層結構。接下來，我們利用樣品震盪磁測儀、磁光柯爾效應儀分析、四點探針裝置、穿透式電子顯微鏡與原理力顯微鏡分析垂直式磁性穿隧元件之各種性質。最後，我們應用熱輔助寫入技術於垂直式磁性穿隧元件並減低自由層的翻轉場。我們在論文最後討論熱輔助寫入垂直式磁性穿隧元件的應用潛力。

Abstract

In this experiment, we used RE-TM materials to prepare magnetic tunnel junctions (MTJ) with perpendicular anisotropy. These RE-TM based p-MTJ could suppress the generation of vortex structures at the edge of the free layers. Therefore, the p-MTJs could be further scaled down to meet the requirement of future generation of magnetic random access memory (MRAM).
The experiment procedure was as follows: First, we presented the complete fabrication processes of p-MTJs, including optimization of AlOX tunneling barriers in conventional MTJs, composition tuning of RE-TM magnetic layers, and finally the preparation of full stacks of p-MTJs. Next, we analyzed the p-MTJ qualities by vibration sample magnetometer (VSM), magneto-optical Kerr effect (MOKE), four-point probe technique, transmission electron microscope (TEM) and atomic force microscope (AFM) etc.. Finally, we introduced the thermally assisted writing technique into p-MTJ to reduce the switching field of the free layers. We discussed the potential and the possibility of thermally-assisted writing p-MTJ in the end of this dissertation.

Contents

Chapter 1 Introduction 1

Chapter 2 Background 3
2-1 Rare-Earth-Transition-Metal (RE-TM) Alloy 3
    2-1-1 Introduction of RE-TM Materials 3
2-1-2 RE-TM materials 3
2-1-3 Magnetization and Coercivity Dependency of RE-TM
Materials 6
2-1-4 Thermomagnetic Properties of RE-TM Materials 8
    2-1-5 Perpendicular Anisotropies of RE-TM Films 9
    2-1-6 Kerr Magneto-Optical Effect of RE-TM Materials 11
2-2 Tunneling Magnetoresistance (TMR) Effect 14
    2-2-1 Spin-Dependent Tunneling (SDT) 14
2-1-2 Magnetic Tunnel Junction (MTJ) and Tunneling Magnetoresistance (TMR) 14
2-3 Magnetic Random Access Memory (MRAM) 19
2-3-1 Overview of MRAM 19
2-3-2 MRAM Device Structure 20
2-3-3 MRAM Read and Write Operation 21
2-3-4 MRAM with Perpendicular Magnetization 23
2-3-5 Thermally Assisted Writing of MRAM 25

Chapter 3 Experiment Procedure 28
3-1 Experiment Flow Chart 28
3-2 Sample Preparation 29
    3-2-1 Dual Ion Beam Deposition System 29
    3-2-2 in-situ Shadow Mask 30
    3-2-3 Plasma Oxidation Chamber 31
  3-3 Analysis Techniques 32
3-3-1 Magneto-Optical Kerr Effect (MOKE) 32
    3-3-2 Vibrating Sample Magnetometer (VSM) 34
    3-3-3 4-Points Probe Station 36
    3-3-4 Atomic Force Microscope (AFM) 37
    3-3-5 Transmission Electron Microscopy (TEM) 39

Chapter 4 Results and Discussion 41
4-1 Introduction 41
  4-2 Standard Longitudinal MTJ 43
    4-2-1 Sample Preparation and Analysis 43
4-2-2 AlOX Thickness Dependence of Longitudinal MTJ 43
4-2-3 Other Parameters Dependence of Longitudinal MTJ 46
  4-3 RE-TM Magnetic Multilayers 48
    4-3-1 Sample Preparation 48
    4-3-2 TM-Rich and RE-Rich Films 50
    4-3-3 RE-TM/CoFe Multilayers 52
  4-4 RE-TM MTJ with Perpendicular Magnetization 57
4-4-1 Half RE-TM p-MTJ 57
4-4-2 Magnetic Property of a RE-TM p-MTJ 61
4-4-3 Transport Property of a RE-TM p-MTJ 64
4-4-4 TEM Analysis of a RE-TM p-MTJ 67


Chapter 5 Conclusion 71

References 73

                                

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