Fabrication and application of giant magnetoresistance spin valve

國 立 高 雄 科 技 大 學 機械工程系博士班 博士論文 巨磁阻自旋閥的製作與應用 Fabrication and Application of Giant Magnetoresistance Spin-Valve 研究生 指導教授 ：鄭春勝 ：鄭振宗 教授 許仁華 教授 中華民國 108 年 月 巨磁阻自旋閥的製作與應用 Fabrication and Application of Giant Magnetoresistance Spin-Valve 研究生：鄭春勝 指導教授：鄭振宗 教授 許仁華 教授 國立高雄科技大學 機械工程系博士班 博士論文 A Thesis Submitted to Department of Mechanical Engineering National Kaohsiung University of Science and Technology in Partial Fulfillment of the Requirements for the Degree of Doctoral of Philosophy in Mechanical Engineering Jan 2019 Kaohsiung, Taiwan, Republic of China ＊National Kaohsiung University of Applied Sciences is the predecessor of National Kaohsiung University of Science and Technology (renamed on Feb 1, 2018) 中華民國 108 年 月 巨磁阻自旋閥的製作與應用 學生：鄭春勝 指導教授：鄭振宗 博士 許仁華 博士 國立高雄科技大學機械工程所博士班 摘 要 關鍵字：磁傳感器，GMR 傳感器，自旋閥，三軸磁力計，電子羅盤，位置 跟踪，渦流探頭。 本研究製作了巨磁阻（GMR）自旋閥裝置，並對其在三軸磁力計，渦流探 頭和位置跟踪中的性能進行了分析。通過使用直流磁控濺射沉積自旋閥 GMR 膜以形成多層結構。本工作中使用的自旋閥結構為 Si / SiO2 | Ta（5nm）| NiFe（3nm）| Co（0.5nm）| Cu（x nm）| CoFe（2.5nm）| IrMn（10nm）| Ta（ 2nm），Cu 層厚度 x = 2.4, 2.6 和 2.8 nm。GMR 自旋閥傳感器係採用掀 離製程將圖案化為 3×100 μm 的磁場敏感元件，頂部的磁通匯聚器層是由 NiFe 材料製成。透過磁阻和 VSM 曲線量測驗證了 GMR 薄膜的傳輸特性，數據 顯示可達成的最大磁阻比約為 8％。三維磁力計的應用使用三個 GMR 傳感器進 行展示，此三個傳感器配置在同一平面上，共用一個磁通導引器。以電磁模 擬分析探討了磁通導引器的磁通彎曲效應，並應用線性變換校準以實現三軸 磁力計的正交感測方向。本研究亦展示了 GMR 自旋閥傳感器的其他應用，包 括使用梯度磁場的位置跟踪系統和用於探傷的渦流探頭。在位置跟踪系統中， GMR 傳感器用於檢測具有 1kHz 正弦波激發梯度場的 z 分量，以相位敏感偵測 器解析同相和正交相位之梯度場 Bi 和 Bq 來確定傳感器的位置，傳感器的座標 顯示在 LabVIEW 編寫的圖形介面軟件上。 GMR 自旋閥傳感器也適用於探傷應 i 用中的渦流探頭，缺陷的位置可由微分缺陷場的最大振幅指出，而深度則可 由微分缺陷場的相位解析。 ii Fabrication and Application of Giant Magnetoresistance Spin-Valve Student: Xuan Thang Trinh Advisors: Prof Jen-Tzong Jeng Co-advisors: Prof Jen-Hwa Hsu Department of Mechanical Engineering National Kaohsiung University of Science and Technology ABSTRACT Keyword: Magnetic sensor, GMR sensor, spin-valve, tri-axis magnetometer, electronic compass, position tracking, eddy current probe In this study, the giant magnetoresistance (GMR) spin-valve devices were fabricated and characterized, and their performance in tri-axis magnetometer, eddy current probe, and position tracking were analyzed The spin-valve GMR film was deposited by using the DC magnetron sputtering system The structure of spin-valve used in this work were Si/SiO2|Ta (5nm)|NiFe (3nm)|Co (0.5nm)|Cu (x nm)|CoFe (2.5nm)|IrMn (10nm)|Ta (2nm) with Cu layer thickness x = 2.4, 2.6, and 2.8nm The GMR spin-valve sensor was patterned into the field sensitive cell of ì 100 àm by using the lift-off fabrication process The flux concentrator layer on the top was made of NiFe material The transport properties of GMR film was demonstrated by magnetoresistance (MR) and vibrating-sample-magnetometer (VSM) data The maximum magnetoresistance ratio achieved was about 8% The application in the three-dimensional magnetometer was demonstrated using three GMR sensors mounted on the same plane with a flux-guide The flux bending effect of flux-guide was analyzed using electromagnetic simulation The linear transform calibration was applied to achieve orthogonal sensing directions for the tri-axis magnetometer The other applications of GMR spin-valve sensors were also demonstrated, including the iii position tracking system using the gradient magnetic field and the eddy current probe based GMR spin-valve sensor for the flaw detection In the position tracking system, the GMR sensor was used to detect the z-component of the gradient field with 1kHz sinewave excitation signal The position of sensor is determined by detecting the inphase and quadrature-phase gradient field Bi and Bq with a phase sensitive detector The coordinates of sensor were displayed on GUI software coded by LabVIEW The GMR spin-valve sensor was also applied for eddy current probe in the flaw detection application The location of the flaws was determined by the maximum amplitude of differential defect field while the depth of the flaws can be determined by the phase of differential defect field iv Acknowledgments Firstly, I would like to thank especially my advisor, Prof Jen-Tzong Jeng, for his guidance and support during my study times at NKUST, Taiwan He is always supportive and gives me the opportunity to expand my knowledge of the fields related to magnetic sensors I would also like to extend my thanks to my Co-advisor, Prof Jen-Hwa Hsu, for his guidance, supports and giving valuable advice for me in my working time at NTU to fabricate GMR sensor as well as his advice for my dissertation Next I would like to thank Prof Lance Horng, Prof Chih-Cheng Lu, Prof Ssu-Yen Huang and Prof Chin-Tai Chen for accepting to be the committee members for my thesis defense I would like to extend my special thanks to all of the members of the Micro Magnetic Technologies Laboratory (MMTLab), Department of Mechanical Engineering at National Kaohsiung University of Science and Technology First, I would like to thank Ph.D Van Su Luong for his introducing me to join MMTLab He has been instructed me to use the equipment in the laboratory, as well as giving me valuable advice during the study and research process Second, I would like to send the special thanks to my Taiwanese in MMTLab, Mr Bor-Lin Lai, Ms Chia-Yi Chang, Mr Wei-Chun Chang, Mr Jyun-Kai Wang, Mr Bo-Chen Chen, Mr Min-Jia Lan, Mr Guan-Wei Huang, Mr Yi-Shian Chiang, Jing-Yuan Chen, and Tsang-Hao Tsao for their help and support to me during the studying time in Taiwan I would like to say a lot of thanks to all of my Vietnamese friends and colleagues at NKUST for sharing and helping me over the past few years Moreover, I also would like to send my thanks to Prof Ssu-Yen Huang and his students in Spintronic Laboratory, they have been helped me many things, as well as facilitating me to use the machines in Spintronic Lab during my working time for fabrication the GMR sensor at Department of Physics, National Taiwan University I would like to thank Prof Chih-Cheng Lu for facilitating me using the devices in Advanced Microsystems and Devices Laboratory (AMD Lab) at Institute of Mechatronic Engineering, National Taipei University of Technology (NTUT) to v pattern the sensors, and my thanks to Mr Chih-Hsien Hung, who was my co-worker in the fabrication for GMR sensor The last thanks, it is indispensable for my great family, for my venerable parents Especially for my beloved wife, Mrs Nguyen Thi Huong, who is always with me and the motivation for me to complete my studies in Taiwan In addition, my work has been supported by the Ministry of Science and Technology of Taiwan under Grant Nos MOST 104-2221-E-151-011, MOST 1042221-E-027-059, MOST 106-2221-E-992 -342, MOST 106-2221-E-151 -025 and MOST 106-2221-E-027 -060 vi Contents ABSTRACT iii Acknowledgments v Contents vii List of Figures x Chapter 1: Introduction 1.1 Applications of magnetic sensor 1.1.1 Induction coil 1.1.2 Fluxgate sensor 1.1.3 Giant Magnetoimpedance (GMI) 1.1.4 SQUID 1.1.5 Hall effect sensor 1.2 Overview of Magnetoresistance 1.2.1 Ordinary Magnetoresistance 1.2.2 Anisotropic Magnetoresistance (AMR) 1.2.3 Giant Magnetoresistance (GMR) 11 1.2.4 Tunnel Magnetoresistance (TMR) 14 1.3 Motivation of study 15 Chapter 2: Fabrication of GMR Spin-Valve 17 2.1 Film structure of GMR spin-valve 17 2.1.1 Spin-valve structure 17 2.1.2 Behavior of GMR spin-valve sheet film 18 2.2 GMR spin-valve fabrication process 19 2.2.1 Patterning methods 19 2.2.2 Photolithography process 21 a Cleaning, coating and soft baking 21 b Exposure 22 c Development and hard baking 22 2.2.3 Film deposition process 23 2.2.4 Patterning using the lift-off method 25 vii Chapter 5: Conclusions and Outlook In the primary research activity in a dissertation entitled “Fabrication and Application of Giant Magnetoresistance Spin-Valve”, the contents presented, discussed and focused in the fabrication techniques for the GMR spin-valve sensors and their application in the design of vector magnetometer with the planar sensing direction, flaw detection using the eddy current probe based on GMR spin-valve sensor The results are summarized as follows: First content of the thesis focused to the structure, working principle and fabrication process of the GMR spin-valve sensors The understanding of the theoretical physics of the spin-valve effect, such as MR ratio, interlayer coupling, and exchange bias, is very important and indispensable for the design and fabrication process of spin-valve sensor The spin-valve structure used in this work is Si/SiO2|Ta(5nm)|NiFe(3nm)|Co(0.5nm)|Cu(xnm)|CoFe(2.5nm)|IrMn(10nm)|Ta (2nm) with the thickness of Cu layer x= 2.4, 2.6, and 2.8 nm For the material of spin-valve structure, the compositions of the ferromagnetic material (FM) used for the pinned layer was found to be Co79.37%Fe20.63%, the FM material for free layer is Ni80.29%Fe19.71%, and AFM layer is Ir28.31%Mn71.69% in atomic percentage To define the sensing direction of the spin-valve sensor, the optimal field annealing temperature is 250°C with the annealing time of hour and the applied magnetic field of 2350 Oe Secondly, the application of GMR sensor is in the design of vector magnetometer The miniature 3D magnetometer was built using the three in-plane GMR sensors, a concentric modulation coil, and a tiny cylindrical tube fluxguide The working principle of this vector magnetometer design is based on the flux bending effect of fluxguide This method enables the ability of the out-of-plane field detection using the in-plane sensing direction The flux bending effect of fluxguide was simulated by the electromagnetic simulation software, 3D-Maxwell Based on the evaluation of fluxgain caused by the bending effect, the dipping angles and the angles between the effective sensing directions were found ϕ = 29.1° and ψ = 98.4°, respectively The 70 linear calibration using the voltage-to-field transform was performed to suppress the non-orthogonality component of the vector magnetometer The effective sensitivities of sensor 1, 2, and of magnetometer, respectively, were calculated to be 130, 129, and 134 V/T The proposed magnetometer was demonstrated in the geomagnetic field as an electronic compass Using the experimental results of the calibration process, the dipping angles and the angles between the effective sensing directions were found to be (ϕ1, ϕ2, ϕ3) = (−31.0°, −28.9°, −32.8°) and (ψ12, ψ23, ψ31) = (95.4°, 97.8°, 94.8°) It is in agreement with the dipping angles and angles of effective sensing direction evaluated by simulation results Next, the application of GMR spin-valve is in the flaw detection The eddy current probe based on the GMR spin-valve sensor was designed and fabricated The probe for the flaw detection system consists of a GMR spin-valve sensor and a square excitation coil The probe was scanned on the surface of a specimen with the different depth of the flaws The experiments were implemented with the different excitation frequency (fexc = 20, 30, 40, and 50 kHz) The in-phase and quadrature-phase output voltage of eddy current sensor was recorded with every fexc The in-phase and quadrature-phase differential defect field was calculated, then the phase of differential defect field was determined and evaluated Based on the differential defect field and the its phase, the position of the flaws and their depths are determined The depth of the flaws is determined based on the change in the phase of differential defect field when the probe scanned toward of the specimen with the increasing the depth of flaws Finally, the magnetic position tracking system with a GMR spin-valve sensor and two sets of magnetic field gradient coils has been investigated The gradient field was generated by providing the 1-kHz sine wave excitation signal for the gradient coils The phase difference of the excitation signal for two gradient coils is 90° When moving the sensor on the detection plane of the gradient coil, the position of sensor is obtained by detecting the gradient field Bi and Bq The linearity correction algorithm was applied to suppress the non-linearity component of the gradient field The obtained sensor’s position is displayed on the GUI software in the real time The 71 average positioning error of this system was found to be 0.696 mm, corresponding to 0.35% on the working range of 200×200 mm The smaller average positioning error is achieved to be 0.21% in the central region corresponding to |x|