Smart Sensors, Measurement and Instrumentation 6
Càndid Reig Susana Cardoso de Freitas Subhas Chandra Mukhopadhyay Giant Magnetoresistance (GMR) Sensors From Basis to State-of-the-Art Applications Smart Sensors, Measurement and Instrumentation
Volume 6
Series Editor Subhas Chandra Mukhopadhyay School of Engineering and Advanced Technology (SEAT) Massey University (Manawatu) Palmerston North New Zealand E-mail: [email protected]
For further volumes: http://www.springer.com/series/10617 Càndid Reig · Susana Cardoso de Freitas, Subhas Chandra Mukhopadhyay
Giant Magnetoresistance (GMR) Sensors
From Basis to State-of-the-Art Applications
ABC Càndid Reig Dr. Subhas Chandra Mukhopadhyay Department of Electronic Engineering School of Engineering and University of Valencia Advanced Technology Burjassot Massey University (Manawatu) Spain Palmerston North New Zealand Susana Cardoso de Freitas INESC-MN Rua Alves Redol Lisboa Portugal
ISSN 2194-8402 ISSN 2194-8410 (electronic) ISBN 978-3-642-37171-4 ISBN 978-3-642-37172-1 (eBook) DOI 10.1007/978-3-642-37172-1 Springer Heidelberg New York Dordrecht London
Library of Congress Control Number: 2013933304
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Editorial
The spintronics concept was stated during the eighties in order to describe charge trans- port mechanisms in which the spin of the electrons play an important rule. The Giant Magnetoresistance effect, reported at the end of this decade, was the definitive step in pushing this concept towards technological applications. Initially, read heads in hard disk drives were benefited of this emerging technology. The bits magnetically saved onto the surface of the disk are read by the binary changing of the resistance of GMR devices. With the time, and taking advantage of the gained knowledge from this re- search, new multilayered structures were engineered in order to make use of the linear capabilities of these devices. Their inherent properties regarding high sensitivity, large scale of integration and compatibility with standard CMOS circuitry have proved def- inite advantages and have placed GMR devices as the preferable magnetic sensors in most of the current applications. This manuscript is dedicated to draw the scope of the state of the art of current mag- netic sensing applications based on GMR sensors. From the definition of the concepts to the analysis of several selected cases of success, the different topics related to this novel technology are described. In the first chapter, the theoretical fundamentals are introduced. The concepts of GMR, spin valve and tunneling magnetoresistance are presented. The descriptions of the physical mechanisms are analyzed, including the sensors based linear regime. The second chapter is dedicated to the involved microfabrication processes. Being multilayered micro-structures, the design and realization of GMR devices share some techniques with standard CMOS processes. Lithography, pattern transfer by lift-off or etching, . . . steps are commonly applied. Other processes such as magnetic layers deposition are specific to GMR technology and their compatibility with standard CMOS processes is a matter of concern. The range of detectivity of the GMR sensors is basically limited by the signal to noise ratio (SNR) instead of the signal level. A detailed description of the noise mech- anisms in GMR sensors is presented in the third chapter. The analysis is particularized to spin valves and magnetic tunnel junctions. The experimental setup for performing VI Giant Magnetoresistance (GMR) Sensors noise measurements is provided. Biasing strategies for minimizing noise effects are also proposed. A GMR sensor can be basically understood as a magnetic resistive sensor. In this sense, the traditional approaches developed for typical resistive sensors can be directly considered. For example, Wheatstone bridges are commonly used in GMR based sen- sors applications. Novel approaches such as current based biasing or resistive array read-out interfaces need to be specifically described. Chapter four analyses the state of the art of resistive sensors interfaces, focusing on GMR particularities and ranging from realization with discrete components to microelectronic designs. Microelectronics in general and the measurement of electric current at the integrated circuit (IC) level is one of the fields in which GMR sensors are applied. After the pre- sentation of the concept (to measure the electric current by means of the associated magnetic field) some cases of success are revised. Particular issues such as bandwidth limitations or self-heating effect are analyzed. Some applications are proposed. The compatibility with non-dedicated CMOS processes is also studied. The automotive world has also incorporated GMR sensors to its portfolio. In this chapter some developments regarding the use of GMR sensors in automobiles at In- fineon are presented. Such sensors can be used in steering angle measurement, rotor position measurement, wheel speed measurement and crank shaft speed. Data acquisi- tion and processing in these systems is also analyzed. Being magnetic sensors and due to their inherent advantages related to miniaturiza- tion, GMR sensors are also applied in compass magnetometers as those included in portable navigation devices such as global positioning systems (GPS) and other mobile gadgets, mainly smartphones. The compass indicates the static orientation of the user which, with the addition of gyroscopic information along with GPS data can give pre- cise location and orientation to the users. In this chapter, the fundamental concepts and the current trends of GMR based compass magnetometers are described. To give an idea of its maturity, GMR sensors have already left the earth and have been included as part of the instrumentation in experimental satellites. In this chapter, the use of commercial off-the-shelf GMR based 3D magnetic sensors on board a picosatellite is described. After a comparison of currently available alternative, the design of the considered system is presented. The system passed all the qualification processes. Highly promising results are being obtained when using GMR sensors in non- destructive evaluation (NDE) processes. Two complimentary chapters are dedicated to this topic. In the first one, the inspection of failures in printed circuit boards (PCBs) is approached. The explanation of the underlying physics (eddy-current testing, ECT), the description of the GMR based scanning probe as well as the associated electronic interface and the analysis of the results, also including finite element modeling (FEM) are treated. In the other chapter, an example of GMR sensors used in biomedicine is described. A needle probe, including GMR sensors is presented. An experimental setup and procedure with agar injected with magnetic fluid to simulate actual clinical process was developed. For improving the performance of NDE processes based on GMR sensors, the use of arrays can be considered. In the last chapter, this approach is analyzed; comparing figures of merit with previously stated systems such as SQUIDs, Hall effect or giant Giant Magnetoresistance (GMR) Sensors VII magnetoimpedance (GMI) based ones. Then the use of magnetoresistive sensors in imaging and scanning microscopy is particularly demonstrated for die level fault isolation. From all described work we can conclude that we can definitively change our ap- preciation on GMR sensors. In few years they have moved from being ‘potential’ to become the first option in much of the applications requiring the sensing of low magnetic fields.
C`andid Reig Susana Cardoso de Freitas Subhas Chandra Mukhopadhyay VIII Giant Magnetoresistance (GMR) Sensors
Dr. Candid` Reig Department of Electronic Engineering Superior Technical School of Engineering University of Valencia
Av. de la Universitat E46100- Burjassot Spain
Tlf. (Office): (+34) 9635 44038 Tlf. (Lab): (+34) 9635 43426 Fax: (+34) 9635 44353 e-mail: [email protected]
Dr. Candid` Reig received the B.Sc. and Ph.D. degrees in Physics from the University of Valencia, Valencia, Spain, in 1994 and 2000, respectively. In 1997, he joined the Department of Applied Physics, University of Valencia, where he developed his doctoral thesis, dealing on properties of semimagnetic semicon- ductors. After one year (2001) as an Assistant Professor within the University Miguel Hern´andez (Elche, Spain), in 2002, he was an Assistant Professor with the Univer- sity of Valencia. Then, he was granted a postdoctoral stay at the INESC-MN (Lisbon, Portugal), working on GMR sensors, focusing on electric current measurement. He is currently an Associate Professor with the De- partment of Electronic Engineering, University of Valencia, where he teaches and does research. His current research interests include the design of novel GMR-based sen- sors for low field applications, their characterization, modeling and the development of integrated microelectronic interfaces. Dr. Reig has participated as researcher and principal investigator in national and international research projects related to magnetoresistive devices and their industrial applications. He has also advised PhD students within these topics. As results, he has published more than 40 journal papers, contributed more than 50 works to conferences and coauthored 4 book chapters. Dr. Reig actively participates in periodic international conference program commit- tees(ICST,SENSORDEVICES, ...), in researchjournals’editorialboards(Sensors andTransducers,MicroelectronicsandSolidStateElectronics,...)aswellasactingas a referee for several research journals. Giant Magnetoresistance (GMR) Sensors IX
Dr. Susana Cardoso de Freitas INESC Microsistemas e Nanotecnologias
Rua Alves Redol, 9 1000-029 Lisboa Portugal
Tlf. (direct line): (+351) 21 3100380 Tlf. (secretary): (+351) 21 3100237 Fax: (+351) 21 3145843 e-mail: [email protected]
Dr. Susana Cardoso de Freitas (born in Sintra, Portu- gal in 1973) received her Ph.D in Physics from Insti- tuto Superior T´ecnico (IST, Lisbon) in 2002, from her studies of GMR multilayers and magnetic tunnel junc- tions for read head and MRAM applications. The re- search was done at INESC (Lisbon). In 2000 she was a “Co-op Pre-Professional Engineer” at IBM, T.J.Watson Research Center (USA). Since 2002 she has been at INESC-Microsystems and Nanotechnologies (INESC- MN), initially as post-doctoral fellow and presently as Senior Researcher, developing ion beam deposition of materials (tunnel junctions and spin valves) on up to 200mm wafers, for application in sensors, biochips and MRAMs. She is the responsible for technology transfer and services related to magneto-resistive sensors and thin film materials and has been involved in several collaborations for magneto-resistive materials optimization and sen- sor fabrication (down to 50nm dimensions), being co-author of several papers on thin film materials, magnetoresistive sensors for biomedical applications, biochips with in- tegrated MR sensors, hybrid MEMS/MR devices or nano-devices for spintransfer. Since 2003 she is also an Invited Auxiliary Professor at the Physics Department of IST (Lisbon), and is responsible for student coordination (over 12 master students, 3 PhD student and 5 post-doctoral fellows). She has coordinated 4 research projects funded by Portuguese Ministry of Sci- ence and Technology (FCT) related to magnetoresistive device optimization, noise characterization, and has been the portuguese responsible for 3 EU Marie-Curie RTN (SPINSWITCH, ULTRASMOOTH, SpinICur) and 1 ICT project (Magnetrodes). She is co-author of 140 publications, 25 conference proceedings and 5 book chapters. X Giant Magnetoresistance (GMR) Sensors
Dr. Subhas Chandra Mukhopadhyay Professor of Sensing Technology, School of Engineering and Advanced Technology,
DISTINGUISHED LECTURER, IEEE SENSORS COUNCIL FIEEE (USA), FIEE (UK) and Topical Editor, IEEE Sensors Journal, Associate Editor, IEEE Transactions on Instrumentation and Measurements, Technical Editor, IEEE Transactions on mechatronics, Postgraduate Advisor, School of Engineering and Advanced Technology, Editor-in-Chief, International Journal on Smart Sensing and Intelligent Systems, (www.s2is.org)
AG-HORT Building AH 3.77 Massey University (Manawatu) Palmerston North New Zealand Tel : +64-6-3505799 ext. 2480 Fax : +64-6-350 2259 email : [email protected] Personal web: http://seat.massey.ac.nz/personal/s.c.mukhopadhyay
Dr. Subhas Chandra Mukhopadhyay graduated from the Department of Electrical Engineering, Jadavpur Uni- versity, Calcutta, India in 1987 with a Gold medal and re- ceived the Master of Electrical Engineering degree from Indian Institute of Science, Bangalore, India in 1989. He obtained the PhD (Eng.) degree from Jadavpur Univer- sity, India in 1994 and Doctor of Engineering degree from Kanazawa University, Japan in 2000. Currently, he is working as a Professor of Sens- ing Technology with the School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand. His fields of interest include Smart Sensors and Sensing Technology, Wireless Sensors Net- work, Electromagnetics, control, electrical machines and numerical field calculation etc. He has authored/co-authored over 270 papers in different international journals and conferences, edited nine conference proceedings. He has also edited ten special issues of international journals and twelve books with Springer-Verlag as guest editor. He is a Fellow of IEEE,aFellow of IET (UK), an associate editor of IEEE Sen- sors journal and IEEE Transactions on Instrumentation and Measurements. He is also a Technical Editor of IEEE Transactions on Mechatronics. He is a Distinguished Lecturer of IEEE Sensors council. He is in the editorial board of many international journals. He has organized many international conferences either a General Chair or Technical programme chair. Contents
Spintronic Phenomena: Giant Magnetoresistance, Tunnel Magnetoresistance and Spin Transfer Torque ...... 1 C. Baraduc, M. Chshiev, B. Dieny
Microfabrication Techniques ...... 31 Diana C. Leitao,˜ Jose´ Pedro Amaral, Susana Cardoso, Candid` Reig Noise in GMR and TMR Sensors ...... 47 C. Fermon, M. Pannetier-Lecoeur
Resistive Sensor Interfacing ...... 71 Andrea De Marcellis, Giuseppe Ferri, Paolo Mantenuto
GMR Based Sensors for IC Current Monitoring ...... 103 Candid` Reig, M.D. Cubells-Beltran´ GMR Sensors in Automotive Applications ...... 133 Konrad Kapser, Markus Weinberger, Wolfgang Granig, Peter Slama
Compass Applications Using Giant Magnetoresistance Sensors (GMR) .... 157 Michael J. Haji-Sheikh Commercial Off-The-Shelf GMR Based Sensor on Board Optos Picosatellite ...... 181 M.D. Michelena High-Spatial Resolution Giant Magnetoresistive Sensors – Part I: Application in Non-Destructive Evaluation ...... 211 K. Chomsuwan, T. Somsak, C.P. Gooneratne, S. Yamada XII Contents
High-Spatial Resolution Giant Magnetoresistive Sensors – Part II: Application in Biomedicine ...... 243 C.P. Gooneratne, K. Chomsuwan, M. Kakikawa, S. Yamada
Magnetoresistive Sensors for Surface Scanning...... 275 D.C. Leitao,˜ J. Borme, A. Orozco, S. Cardoso, P.P. Freitas
Author Index ...... 301 Spintronic Phenomena: Giant Magnetoresistance, Tunnel Magnetoresistance and Spin Transfer Torque
C. Baraduc, M. Chshiev, and B. Dieny
SPINTEC UMR8191, CEA-CNRS-UJF-INPG, 17 rue des martyrs, Grenoble, France {claire.baraduc,mair.chshiev,bernard.dieny}@cea.fr
Abstract. This introduction to spintronic phenomena deals with the three major physical effects of this research field: giant magnetoresistance, tunnel magnetoresistance and spin transfer torque. This presentation aims at describing the concepts in the simplest way by recalling their historical development. The correlated technical improvements mostly concerning material issues are also described showing their evolution with time.
In recent decades, progress in fabrication and characterization of systems with reduced dimensionality has stimulated fundamental research on a wide range of quantum phenomena and has enabled development of nanomaterials with new functionalities related to new information technologies. The most remark- able event, in this context, is the discovery of giant magnetoresistance (GMR) in magnetic multilayered structures in 1988 by the groups of A. Fert [1] and P. Gr¨unberg [2]. They observed a significant change in the resistance of multi- layers when the magnetizations of adjacent ferromagnetic layers separated by a nonmagnetic spacer were brought into alignment by an applied magnetic field. In other words, they showed that the electron flow through the structure is con- troled by the relative orientation of magnetizations in adjacent layers similarly to a polarizer/analyzer optical experiment (Fig. 1). The discovery of this spin filtering effect opened new ways of exploring magnetic properties of materials by means of spin-dependent transport and generated a new field of research called spin electronics or spintronics [3,4,5,6], which combines two traditional fields of physics: magnetism and electronics. In other words, it is not only the electron charge but also the electron spin that is used to operate a device. Spin is the intrinsic angular momentum of a particle which, in the case of the electron, is characterized by a quantum number equal to 1/2 with two possible states called “spin-up” and “spin-down” (or “majority” and “minority”). In ferromagnetic materials, the Coulomb interaction and Pauli exclusion principle cause a long- range ordering of the unpaired up (or down) spins leading to the finite magnetic moment μ per unit volume (magnetization M) resulting from the difference of majority and minority density of states (DOS). Furthermore, such inequality of the DOS for two spin states at the Fermi surface leads to significantly different conductivities for the spin up and the spin down electrons as was demonstrated by A. Fert and I. Campbell in the late 1960s [7, 8]. Along with the existence
C. Reig et al.: Giant Magnetoresistance (GMR) Sensors, SSMI 6, pp. 1–30. DOI: 10.1007/978-3-642-37172-1_1 c Springer-Verlag Berlin Heidelberg 2013 2 C. Baraduc, M. Chshiev, and B. Dieny of the long range interlayer coupling between two ferromagnets separated by a nonmagnetic spacer [9], these observations were the key steps in the discovery of GMR suggesting that the transport in ferromagnetic materials is spin-dependent and can be considered within the two current model [10]. Giant magnetoresis- tance became the supreme manifestation of spin-dependent transport and was recognized by the award of the Nobel Prize 2007 to A. Fert and P. Gr¨unberg.
Parallel configuration Antiparallel configuration
Fe Cr Fe Fe Cr Fe
Equivalent resistances :