磁阻式隨機存取記憶體(Magnetoresistive Random Access Memory, MRAM)在二十一世紀開始展露頭角，相較於現今普遍流通於市面的動態隨機存取記憶體(Dynamic Random Access Memory, DRAM)，MRAM擁有低耗能以及非揮發性的特點，這使得MRAM躍上了新世代記憶體的舞台，而其中磁性穿隧接合(Magnetic Tunnel Junction, MTJ)更是在MRAM中扮演了不可或缺的角色，本研究旨在開發出具有垂直異向性的MTJ並且對MTJ做電性分析。
本文藉由高真空磁控濺鍍機以及高真空退火系統來製備MTJ所需要的薄膜結構，在得到MTJ所需要的垂直異向性之後，藉由X射線繞射分析儀以及穿隧式電子顯微鏡來檢測MTJ中穿隧層(MgO)是否擁有001結晶方向， 穿隧層的001結晶方向是決定磁阻率大小的重要因素，接下來便進入製作元件的階段。
元件的製作藉由黃光微影以及離子束蝕刻的技術來得到我們所需要的圖形，然後利用兩點探針測量來量測在外加磁場下元件的電阻變化，再去換算成磁阻率，最終在Ta-based MTJ上得到了65%的磁阻率，由於在Ta-based的MTJ中的CoFeB並沒有結晶，所以為了可以利用CoFeB的結晶來提高磁阻率，我們引進了鉬(Mo)來取代Ta使得整個膜層結構可以承受更高溫的退火來迫使CoFeB結晶，然而因為蝕刻參數未能優化，我們並沒有辦法在Mo-based MTJ上量測到磁阻率的大小。
因為在Mo-based MTJ所遇到的製程瓶頸，我們使用Peak Force Tunneling AFM (PF-TUNA) 來做MTJ的電性分析，PF-TUNA 如同Conductive AFM一般可以做電性分布的量測，最終我們能夠利用此分析工具來剖析我們MTJ製程上的問題。

Magnetoresistive Random Access Memory (MARM) has emerged as a prospective memory in 21st century. Compared to other memories, such as DRAM SRAM, MRAM possesses the advantages of low power consuming and non-volatile which makes it so attractive. Magnetic Tunnel Junction (MTJ) plays an indispensable role among all the components in MRAM. In this research, we aim to develop a MTJ with perpendicular anisotropy (PMA) and also do the electrical analysis of MTJ.
We prepared the MTJ film by ultra high vaccum magnetron sputtering and annealed the samples in high vaccum annealing furnace to obtain good PMA. After the optimization of magnetic properties, we need to know whether the tunneling barrier (MgO) has a (001) crystallization orientation or not since the (001) orientation is a key factor to determine the TMR ratio. We used X-ray diffractometer (XRD) and Transmission electron microscope (TEM) to characterize the crystallization orientation of MgO.Next, we start to fabricate the MTJ devices to measure the Tunnel magnetoresistance (TMR) ratio.
In our MTJ processing, we first used the photolithography to define our MTJ pattern and then we etched our MTJ devices through Ion beam etching (IBE). After all the processsings were done, we measured the TMR by two points probe measurement with an external field perpendicular to our film. Finally, we cauld achieve a 65% TMR ratio on our Ta-based MTJ but this result is not good enough compared to other researchs.There are several reasons for this, the most possible reason is that our CoFeB did not crystallize in our Ta-based MTJ. In order to force the CoFeB to crystallize, we need to increase our annealing temperature but after we increase annealing temperature, we lost PMA on Ta-based MTJ. Hence,we introduced Mo to replace Ta to attain high annealing temperature and maintain good PMA simultaneously. Nonetheless, since we had not optimized our etching recipe for Mo-based MTJ, we were not able to learn how much TMR ratio we can obtain in Mo-based MTJ.
Owing to the bottleneck we faced in Mo-based MTJ, we utilized Peak Force Tunneling Atomic Force Microscope (PF-TUNA) to analyze the electrical properties of MTJ. PF-TUNA functions as Conductive Atomic Force Microscope (C-AFM) and it can analyze the distribution of electrical properties on our MTJ devices. At last, we can use this analyzing tool to dissect our issue on MTJ processing.

Abstract ii
摘要 iv
目錄 vi
第ㄧ章 前言 1
第二章 文獻回顧 2
2.1 自旋電子學(Spintronics) 2
2.2 穿隧磁阻效應(Tunneling Magnetoresistance,TMR) 3
2.3 CoFeB-MgO結構的起源 5
2.4 具垂直異向性的CoFeB-MgO結構 8
2.5 雙層CoFeB/MgO結構 11
2.6 電流感應磁矩翻轉(Current induced magnetization switching) 12
2.7 自旋轉移矩(STT) 14
2.8 阻尼常數(Gilbert damping constant) 15
2.9 臨界電流密度 17
2.10 退火製程及氧化鎂穿隧層對磁阻率的影響 18
第三章 實驗設備與量測儀器 23
3.1高真空磁控濺鍍系統 23
3.2高真空退火系統 24
3.3黃光微影製程 (Photolithography) 25
3.4離子束蝕刻系統 (Ion Beam Etcher) 26
3.5振動樣品磁測儀 (Vibrating Sample Magnetometer) 27
3.6原子力顯微鏡 (Atomic Force Microscopy) 28
3.7 兩點探針量測平台 29
第四章 實驗結果與討論 30
4.1 Ta-based MTJ磁性質調控 30
4.2 MgO結晶性的優化 36
4.3 Ta-based MTJ元件製作與穿隧磁阻的量測 38
4.4 Mo-based MTJ磁性質調控 39
4.5 MTJ的電性分析 43
第五章 結論 48
參考文獻 49

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