【作者】 陈磊；

【导师】 周勇；

【作者基本信息】 上海交通大学 ， 微电子学与固体电子学， 2011， 博士

【摘要】 磁传感器广泛应用于航空航天、自动化测量、磁性存储、生物医学等各行业中，扮演着重要角色。巨磁阻抗(Giant Magnetoimpedance, GMI)效应作为一种新型磁传感技术，它能够弥补巨磁阻(Giant Magnetoresistance, GMR)传感器的不足，实现在很宽温度范围下对微弱磁场的快速灵敏测试，同时它的制作成本较低，容易实现微型化和集成化，是一种能够同时满足灵敏度高、微型尺寸、响应速度快、功耗低和无磁滞等信息技术要求的传感器。相对于薄膜和薄带材料而言，非晶丝材比较容易制备，易于形成理想的磁各向异性，能够获得较为理想的敏感性和GMI性能，但是丝材存在着明显的缺点：大批量生产时难以保证样品性能的可重复性，与电路的焊接、安装比较困难等。而通过工艺手段的改进，薄膜和薄带材料目前在GMI性能和磁场敏感性方面已经达到甚至超过非晶丝材，同时二者的制作工艺能够与大规模集成电路(Integrated Circuit，IC)相兼容，批量生产时能够保证样品性能的可重复性，制作成本较低，与电路的焊接和安装比较方便。对单层和多层结构薄膜与薄带材料中的GMI效应，人们开展了相关的理论研究，但是理论研究的过程都进行了简化，没有考虑到材料中各向异性场、易轴取向和阻尼系数对GMI效应的影响，同时对于曲折状结构的薄膜与薄带材料，还没有相应的理论模型对其GMI效应进行描述。对于薄膜和薄带GMI传感器的制备，很多研究小组采用手工裁剪或金属掩膜图形化的方法进行制备，缺乏对MEMS制备工艺的系统研究，难以保证样品的性能稳定性和批量化生产。在生物检测方面，科学家已经开始了基于GMI传感技术的相关研究，但到目前为止，尚未见到针对某个具体病原体的、基于巨磁阻抗传感器的应用型检测体系。同时，目前基于GMI效应的生物检测尚处于起步阶段，涉及到为数不多的细胞实验都是利用细胞样品具有的吞噬作用与磁性粒子进行结合，未有对某一种细胞样品进行特异性检测。基于以上考虑，本文对基于软磁薄膜和薄带材料的微型GMI传感器开展理论、制备工艺和生物检测应用方面的研究，将基于MEMS工艺制备的高性能GMI传感器应用于生物检测领域，通过实验工作，为建立一套相对完善的、基于GMI效应的生物检测系统打下基础。本论文的主要研究工作如下：1．从麦克斯韦方程和磁化强度进动方程出发，根据电磁场在导体中的分布以及铁磁体中磁化强度在高频下的进动模式，建立了单层、曲折状和三层夹心结构铁磁材料阻抗计算的理论模型。在建立的模型中，考虑了包括各向异性场、阻尼系数和易轴取向等在内的诸多影响参数，根据材料和测试的实际情况设立了坐标系和边界条件，使理论模型得到符合实际情况的简化，同时保证计算得到的理论结果能很好地与实验数据进行对照；2．运用所建立的理论模型，对单层、曲折状和三层结构中的GMI效应进行了系统的模拟计算，采用MATLAB软件辅助进行符号与数值运算，解决了方程初始变量较多、方程不便求解的问题。通过理论计算研究了材料的结构、尺寸效应、电流频率、外加磁场、各向异性场、易轴取向以及阻尼系数等因素对GMI效应的影响。理论模拟计算表明，材料结构、电流频率、外加磁场、样品尺寸、各向异性场、易轴取向和阻尼系数均对GMI效应的幅值和磁场灵敏度有显著影响，而各向异性场和易轴取向还改变GMI曲线的变化规律，决定GMI正向峰值的大小和出现与否；3．采用制备的NiFe薄膜和商品化Co基非晶薄带作为GMI传感器材料研究对象。采用磁控溅射方法制备了NiFe薄膜，研究了溅射条件如Ar气流量、溅射功率、溅射气压等对材料磁性能的影响，获得了制备NiFe薄膜的最佳工艺条件。采用多种材料测试分析手段，如X-射线、扫描电子显微镜(SEM)测试了薄膜和薄带材料热处理前后的元素组份和微观结构，利用振动样品磁强计（VSM）对薄膜和薄带材料进行软磁性能分析。测试结果表明，NiFe薄膜和Co基薄带材料具有优异的软磁性能，为获得高性能的GMI传感器提供了保障；4．采用射频溅射、光刻、电镀、离子束刻蚀等与大规模集成电路相兼容的微细加工工艺制备了单层、三层、单条状和曲折状NiFe薄膜结构，并对其GMI效应进行系统研究。结果表明：气流量和溅射气压对薄膜GMI性能有重要影响，通过实验得到薄膜溅射的最优条件组合为：功率600W，Ar气流量14sccm，溅射气压5.4×10-3Torr；NiFe/Cu/NiFe曲折状三层结构中得到最大的GMI变化率为34%，磁场灵敏度为1.5%/Oe；5．采用键合、光刻、化学刻蚀和电镀等微细加工工艺制备了单条状和曲折状Co基非晶薄带结构，并对其GMI效应进行系统研究。结果表明：曲折状3匝结构的薄带材料中得到最大的GMI变化率为204%，磁场灵敏度为17.8%/Oe，3匝结构的线宽为800μm，线条间距为400μm，同时单条状和曲折状Co基非晶薄带材料中GMI效应的试验结果与理论结果有很好的符合；6．设计了一种基于纳米磁性微球标记物的微生物芯片系统，结合GMI检测技术用于HPV 16/18病毒的分型检测。利用纳米磁性微球良好的磁操控性，将HPV保守区双链扩增片段方便地分离成单链片段，同时将纳米磁性微球标记的单链扩增片段直接用于随后的GMI传感器分型检测，将以往的分离、检测标记步骤合二为一。通过生物芯片中HPV病毒检测区域与阴性检测区GMI检测信号的差异，成功实现对HPV病毒的分型检测。在对132份临床宫颈拭子样本的检测中，以DNA测序为金标准，灵敏度均达到95%以上，其中特异性均为100%；7．选用RGD环肽作为胃癌细胞中αvβ3整合素的靶向配体，经过表面修饰的Fe3O4纳米粒子作为磁性标记物，利用GMI检测技术和细胞靶向标定技术对不同胃癌细胞样本进行检测，结果表明：GMI传感器不但能够检测到胃癌细胞中是否吸收了磁性纳米粒子，而且可以检测出样本是否为靶向标定过的胃癌细胞，将靶向标定的胃癌细胞与健康细胞以及仅仅通过吞噬方式吸收磁性粒子的胃癌细胞区分开来，与之前基于GMI效应的生物检测相比，将GMI的检测从非特异性检测推进到了特异性检测。更多还原

【Abstract】 Magnetic sensors are widely used in aerospace, automatic measurement, magneticstorage, biomedical etc and play an important role. As a new type of magnetic sensortechnology, giant magnetoimpedance (GMI) effect can make up for the insufficiency ofgiantmagnetoresistance (GMR) sensor to achieve a rapid and sensitive test with widetemperature range in weak magnetic field. While GMI effect is the only one able to meetinformation technology requirements of the sensor with high sensitivity, miniature size,fast response, low power consumption, no hysteresis, low production cost, easyminiaturization and integration. Compared to the film and ribbon material, the amorphouswire is easy to fabricate, easy to form an ideal magnetic anisotropy and easy to obtain anideal sensitivity and GMI performance, but wire material also has the obvious drawback:difficult to ensure repeatability of the sample performance in large quantities production,difficult for circuit welding and installation and uncompatible to large scale integratedcircuit (IC) technology. GMI performance and field sensitivity of film and ribbon materialhas been reached or even exceeded the amorphous wire through technical improvement,while the production process of them are compatible with IC, ensure the reproducibility ofthe sample performance in mass production, low production costs and the circuit weldingand installation are convenient. Some theoretic research works have been done toinvestigate the GMI effect in thin film and ribbon with single layered and multi-layeredstructure, but the theory model of GMI effect in meander structure is still lack. Inbiological detection, several investigations based on GMI sensing technology are carriedout, but so far, it has not seen one detection system based on giant magneto-impedanceeffect completely developed and clinical evaluation for specific pathogens. Meanwhile, thecurrent biological detection based on GMI effect still remain in the non-specific phase, only a small number of cells experiments have been done. The combination of cells andmagnetic particles in these experiments are phagocytosis and it can not be a specificdetection for a certain kind of cells.Based on the above considerations, systemically investigations for theory, fabricationand applications in biological detection of GMI micro sensors based on soft magnetic thinfilms and ribbon materials are carried out in this thesis. The GMI sensors with excellentperformance are picked out in order to establish a complete biological detection system forbiological testing and clinical application. The main research works of this thesis are asfollow:[1] From the Maxwell equations and the equation of magnetization motion, weestablish the theoritical model to calculate the impedance of ferromagnetic materials withsingle layered, meander and trilayered structure according to the distribution ofelectromagnetic field in ferromagnetic conductor and magnetization motion model at highfrequencies. In the model, many of parameters, such as the anisotropy field, the dampingcoefficient and the easy axis orientation etc, are considered. Coordinate system andboundary conditions are established according to the actual situation of the GMI sensor.The theoretical model is simplified consistent with the actual situation and ensuring thatthe theoretical results can be compared very well with the experimental data;[2] GMI effect in ferromagnetic materials with single layered, meander and trilayeredstructure are calculated using the established theoretical model. Symbolic and numericalcomputations are assisted by MATLAB software. Effects of the structure of the material,size effect, current frequency, magnetic field, anisotropy field, easy axis orientation and thedamping factor on the GMI effect are investigated by the theoretical calculation.Theoretical simulation results show that the sensor structure, current frequency, magnticfield, the sample size, the anisotropy field, easy axis orientation and the damping effecthave significant influences both on the magnitude and field sensitivity of the GMI effect.Also the GMI curves are changed by anisotropy field and easy axis orientation and todecide the size of the positive peak of GMI and the emergence or not;[3] Sputtered NiFe film and the commercialization Co-based amorphous ribbons were used for the GMI sensor materials. NiFe film was prepared by magnetron sputtering. Theinfluence of sputtering parameters, such as Ar gas flow rate, sputtering power andsputtering pressure, on magnetic properties of NiFe thin films are investigated and theoptimum sputtering conditions are obtained. Analysis method, such as X-rays, scanningelectron microscopy (SEM) and vibrating sample magnetometer (VSM), was adopted totest material component, surface microstructure and soft magnetic properties. The resultsshow that, NiFe and Co-based thin film materials exhabit excellent soft magneticproperties which guarantees to obtain high-performance of the GMI sensors;[4] NiFe film with different structure are fabricated by RF sputtering, lithography,electroplating and ion beam etching technology and the GMI effect of them are studied.The results show that: gas flow rate and sputtering pressure have a major impact on theGMI performance of thin film. The optimal parameter conditions are obtained through theexperiments: sputtering power 600W, Ar gas flow 14sccm, sputtering pressure5.4×10-3Torr; trilayered NiFe/Cu/NiFe with a three turns meander structure has GMI ratiois 34% and GMI field sensitivity was 1.5%/Oe;[5] Co-based amorphous ribbon with different structure are fabricated by bonding,lithography, chemical etching, and electroplating micro-fabrication process and the GMIeffect are studied. The results show that: the meander structure of ribbon with 3 turns hasmaximize GMI ratio of 204% with the magnetic field sensitivity of 17.8%/Oe, the linewidth of 3 turns structure is 800μm, the line spacing of 400μm. Meanwhile, experimentalGMI effects in Co-based amorphous ribbon are fit well with theoretical results;[6] Microbial typing system for HPV 16/18 virus is designed based on nano-magneticbeads marker. Conserved double-stranded amplified segment of HPV can be easilyseparated into single-stranded fragments by fully use of the good handling ofnano-magnetic magnetic microspheres. While the magnetic signal of the nano-magneticbeads labeled single-chain fragment was directly deteceed by GMI sensor and used forsubsequent genotyping. The separation and detection steps of previous typing method aremerged into one tag. DNA sequencing used as the gold standard in the clinical detection of132 cervical swab samples, the sensitivity of 95% and specificity of 100% of them; [7] RGD cyclic peptide used as the targeting ligands ofαvβ3 integrin in gastric cancercells, the surface modified Fe3O4 nanoparticles used as magnetic marker in detection.Targeted detection of different gastric cancer cells are carried out using GMI sensor, thetest results show that: GMI sensor can detect not only whether the cancer cells absorb themagnetic nanoparticles, but also can detect whether the target samples is gastric cancercells by targeting. Targeted gastric cancer cell, healthy cells and the gastric cancer cell toabsorb magnetic particles by phagocytosis can be recognized successfully. Compared withthe previous biological detection based on GMI effect, the GMI detection are improvedfrom the non-specific to the specific detection.更多还原