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學校名稱輔仁大學
系所名稱物理學系
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學號487326099
研究生(中)高禕璟
研究生(英)I-Ching Kao
論文名稱(中)研究可用於穿隧磁阻效應之氧化鋁層的製作及其物性
論文名稱(英)Fabrication and physical property studies of Al oxidation layer used in spin-dependent tunneling junction
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指導教授(中)姚永德
指導教授(英)Yeong-Der Yao
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學位類別碩士
畢業學年度88
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關鍵字(中)氧電漿氧化法 穿隧磁阻效應 磁阻記憶體 乾氧化法 濕氧化法 氧化深度 自然氧化法 真空內電阻量測
關鍵字(英)oxygen plasma oxidation TMR MRAM Dry oxidation Wet oxidation oxide depth nature oxidation in-situ resistance measurement
摘要(中)我們在7059 Corning glass基板上濺鍍Al薄膜,將Al薄膜以乾氧氣和氧電漿氧化的方式製作Al及Al-O,並觀察多層鋁與單層鋁在此過程中不同的結果。我們以LR-400及四點量測法量測樣品在真空室內製程與氧化的電性,以AFM(atomic force microscopy)觀察樣品表面粗糙度,以X-ray分析薄膜之結構。 對於Al在厚度對電阻率的影響上,F-S模型(Fuchs-Sondheimer model)及修正後的F-S模型均不易解釋我們的結果;因此我們以半經驗的電阻公式來分析我們的數據。我們發現對於自然氧化而言,Al在不同的乾氧氣壓力下,其氧化的深度約1nm以下;這與在空氣中水氣造成的溼氧化,其深度大於5nm;有非常明顯的不同。在氧電漿氧化上,其氧化深度將深層氧化在自然氧化形成的保護層,一般氧化的深度約1nm。且在氧電漿時間約十多分鐘後將由於氧離子擴散程度與Al厚度的平衡關係,而使氧化達到穩定態。 我們以最佳的氧化條件來製作自旋相關穿隧接面(spin-dependent tunnel junction, TMR),而AFM、TEM(transmission electron microscopy)、和X-ray結果顯示絕緣層為平整的連續薄膜、低粗糙度和無序狀態,並以MOKE和四點量測觀察元件之磁性、磁阻和I —V曲線。我們發現約1 eV的位能障高、2.2nm的位能障寬、不互相耦合的上下鐵磁性層、及約8%的穿遂磁阻值,顯示我們的氧化鋁層具有可應用在TMR上的價值。
摘要(英)The in-situ electrical characterization of Al thin films (< 20 nm), which were fabricated by magnetron sputtering system, was performed by AC resistance bridge measurement. Further, we studied variations of electrical properties of oxidized Al thin films by pure oxygen gas and oxygen plasma, respectively. The AFM (atomic force microscopy) images and X-ray diffraction were used to measure our sample morphology and crystalline structure information. We found that the F-S model (Fuchs-Sondheimer model) and the modified F-S model, which considers the roughness influence on F-S model, does not explain our results exactly. We used semi-empirical formula to fit our data to discuss the variation of the resistivity under oxidation. The oxidation depth of Al is about 1nm for dry oxidation of Al. This is different from the wet oxidation of Al, which is larger than 5nm. The depth of Al-O prepared by oxygen plasma oxidation of Al is stable to about 1nm after ten to twenty minutes. The stabilized thickness of Al-O is due to the competition of the diffusive depth of oxygen ions and the resistive distance by Al-O layer. In the application, we fabricated spin-dependent tunnel junction (TMR) with our best condition of preparation of Al-O, and measured their cross-section structure, surface topography, and crystalline structure by TEM (transmission electron microscopy), AFM, and X-ray, respectively. TMR junction with the low interface roughness (~0.9nm) and amorphous structure of 26Å thickness of Al-O has the following properties: 1 eV of barrier height, 2.2nm of barrier width. We had used above technology to fabricate TMR junction with independent magnetic behavior, and 8% of TMR ratio. Hence, the preparation of Al-O by our method can be appreciated to the fabrication of TMR successfully.
論文目次誌謝...........................................................I 摘要...........................................................i Abstract......................................................ii 目錄.........................................................iii 圖目次.........................................................v 表目次........................................................ix 第一章 前言....................................................1 第二章 理論簡介................................................3 第1節 電漿理論.................................................3 第2節 薄膜理論簡介.............................................8 第3節 射頻電漿氧化法簡介(RF plasma oxidation technology)......11 第三章 實驗設備原理...........................................17 第1節 濺鍍原理................................................17 第2節 四點量測法..............................................20 第3節 X-ray原理...............................................23 第4節 原子力顯微鏡原理(Atomic Force Microscopy, AFM)..........26 第四章 樣品的製作與DATA的分析.................................31 第1節 樣品的製作..............................................31 第2節 DATA的分析..............................................36 第五章 實驗結果與討論.........................................45 第1節 多層鋁組成之厚膜在成長方向與速率之變因..................45 第2節 單層鋁薄膜的電性........................................54 第3節 單層鋁薄膜的氧化機制....................................58 第4節 應用....................................................69 第六章 結論...................................................77 參考文獻......................................................79 附錄..........................................................81
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