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研究生:陳柏羽
研究生(外文):Bo-Yu Chen
論文名稱:用於自旋轉移力矩翻轉之導電式原子力顯微鏡探針特性研究
論文名稱(外文):The characterization of conductive atomic force microscopy probe-tips characterization for spin-transfer switching
指導教授:吳德和
指導教授(外文):Te-ho Wu
學位類別:碩士
校院名稱:國立雲林科技大學
系所名稱:材料科技研究所
學門:工程學門
學類:材料工程學類
論文種類:學術論文
論文出版年:2012
畢業學年度:100
語文別:中文
論文頁數:100
中文關鍵詞:接觸電阻自旋轉移力矩探針磨損導電式原子力顯微鏡
外文關鍵詞:Conducting atomic force microscope(Conducting AFContact resistancespin transfer torque (STT)Wear of probe
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摘要
導電式原子力顯微鏡(Conductive Atomic Force Microscope; CAFM)為檢測奈米鑄型磁穿隧接面之自旋轉移力矩(spin-transfer-torque; STT) 磁化翻轉的方法之一,本檢測方法較以往CIPT(current-in-plane tunneling)或位元化後四點探針檢測技術來的簡單且不易造成元件毀損,然而導電式探針針尖的磨耗與接觸電阻的問題對自旋轉移翻轉而言是極重要的關鍵之一。因此,本論文主要探討當探針上濺鍍不同金屬材質與膜厚時,對其掃描過程之損耗效應的影響,包含其:磨損機制、磨損所造成的針尖變形對STT檢測過程中位元定位及接觸電阻之影響。研究中以SEM觀察探針針尖的變化、利用AFM掃描來探討不同金屬厚度對定位精準度之影響。
在不同金屬材質之測試方面,由於鉑(Pt)金屬之導電性較佳、耐磨度較高、且氧化速度較慢,故較適合用於提升AFM探針之耐電流值以進行STT測試。而在不同Pt金屬厚度的測試中,Pt金屬厚度為100 nm-200 nm,發現Pt金屬厚度對接觸電阻影響不大,接觸電阻值約為40±2 Ω。且以濺鍍100 nm Pt金屬之探針進行STT測試,在脈衝寬度為5 μs的情況下,其耐電流值達5 mA。此外,經由磨損測試可得知Pt金屬之磨損速率約為4.1 nm/mm,而接觸電阻值隨磨損測試長度增加而提升。在磨損測試過程中發現隨著Pt金屬的減少,原本的Si針尖將逐漸裸露,導致Pt層的接觸面積相對減少而造成接觸電阻大幅增高。其中Pt金屬厚度為200 nm時,其Si針尖在磨損測試長度達40 mm開始裸露;而Pt金屬厚度為100 nm時,則是磨損測試長度達30 mm開始。因此,不僅可減少以往探針製備成本也提高探針在STT量測時定位元件的精確性且據實驗統計表,依照磨損程度不同所產生之接觸電阻取得受測物本身之電阻值以及推測探針壽命,此結果將有助於改善利用CAFM量測自旋轉移力矩翻轉之問題。
Abstract
Conducting atomic force microscope (Conducting AFM or CAFM) has been used to measure the magnetization switching induced by spin transfer torque (STT) for nanopillars of magnetic tunnel junctions of one of the methods. This detection method is more simple compared to the previous CIPT(current-in-plane tunneling) or four-point probe detection technology, and difficult cause component damage, however, the wear and contact resistance problem of the conductive probe tip for the magnetization switching induced by STT is one of the very important key. Therefore, this study focuses on discussion the different metal materials and thickness on the probe by the sputter, for the wear effect on the scanning process, including: the probe wear mechanism, wear caused by the probe tip deformation of the effect of the component location in the detection process and contact resistance.The study by SEM to observation on the probe tip changes, and discuss the effect of different metal thickness on the component location accuracy of AFM scanning.
In terms of testing of different metallic materials, because Platinum(Pt) has better conductivity, high wear resistance, and oxidation is slow, therefore, is more suited to useing to upgrade the resistance of the AFM probe current value on the STT test. On the different Pt metal thickness testing, Pt metal thickness is 100 nm-200 nm, found the Pt metal thickness has little effect on contact resistance, the contact resistance value of about 40±2 Ω. Use Sputtering 100 nm of Pt metal probe in STT test, in this case of a pulse width of 5 μs, it’s resistance to current value is 5 mA. In addition, through the wear test can be known Pt metal wear rate of about 4.1 nm/mm, and the contact resistance values increases with increasing wear test length. And found Pt metal decrease in the wear testing process, original Si tip would be gradually exposed, result in the contact area of the Pt layer relative reduction caused by the contact resistance significantly increased. When Pt metal thickness of 200 nm, the Si tip began to exposed on the wear test length up to 40 mm; while the Pt metal thickness of 100 nm, the Si tip began to exposed on the wear test length up to 30 mm. Therefore, Not only can reduce the cost of probe preparation but also can according to the experimental tables, to improve the accuracy of probe positioning components in the STT measurement, in accordance with the different the degree of wear arising on contact resistance and obtain resistance value by the measured material and speculated of the probe lifetime, this result will help to improve problem by the use of CAFM measured spin transfer torque.
摘要 i
Abstract iii
誌謝 v
目錄 vi
圖目錄 viii
表目錄 xi
第一章 緒論 1
1.1 研究背景、動機與目的 1
1.2 論文架構 3
第二章 理論背景 4
2.1 自旋轉移力矩(Spin-Transfer Torque) 4
2.1.1 自旋轉移力矩機制 6
2.1.2 文獻回顧 10
2.2 AFM探針之變形與磨損機制 14
第三章 實驗設備與流程 23
3.1 實驗流程 23
3.2 實驗設備 26
3.2.1 六靶式高真空射頻直流磁控反應式濺鍍系統 26
3.2.2 掃描式電子顯微鏡 (Scanning Electron Microscopy;SEM) 27
3.2.3 原子力顯微鏡 (Atomic Force Microscopy;AFM) 28
3.2.4 X光繞射分析儀 (X-Ray Diffraction;XRD) 29
3.2.5 交替梯度磁測儀 (Alternative Gradient Magnetometer;AGM) 30
3.2.6 自旋轉移力矩量測平台 31
第四章 結果與討論 33
4.1 探針製備 33
4.1.1 以不同金屬材料製作探針 35
4.1.2 探針耐電流測試 52
4.2 探針之接觸電阻 63
4.2.1 探針與薄膜接觸電阻測試 65
4.2.2 探針與元件接觸電阻測試 67
4.3 探針磨耗測試 70
第五章 結論 82
第六章 未來展望 82
參考文獻 84
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