Tunneling Magnetoresistance Devices with MgO barrier and CoFeB electrodes for Magnetic. Field

Transcription

1 Tunneling Magnetoresistance Devices with MgO barrier and CoFeB electrodes for Magnetic Field Sensors Piotr Wiśniowski Michał Dąbek Department of Electronics AGH-University of Science and Technology NANOSPIN-Meeting, , Kraków 1/27

2 Plan I.Introduction (3-11) Applications of High Sensitivity Sensors Properties of CoFeB/MgO/CoFeB Devices II.CoFeB/MgO/CoFeB Devices (12-27) Sensing Problems-Solutions Dynamic Properties III. Summary NANOSPIN-Meeting, , Kraków 2/27

3 Applications of High Sensitivity Sensors Biosensing Biomolecules (Toxin,Viruses) Magnetocardiography (Heart) Fault Localization in IC Current/Field Distribution Mapping Mass Storage Hard Disk Drives Electronic Equipment-Compass Earth Magnetic Field Automotive Speed, Angle, Current nt - ft nt - pt nt to pt T (Kraków 49 ) mt- T I. Introduction NANOSPIN-Meeting, , Kraków 3/27

4 Applications of High Sensitivity Sensors Biosensors Detection of magnetically labeled nanoparticles Biotoxin (water, food) INESC-MN Volume of the nanoparticles I. Introduction NANOSPIN-Meeting, , Kraków 4/27

5 Applications of High Sensitivity Sensors Fault Localization in Integrated Circuit Field Mapping in Faulty Areas Fabrication Fault of ASIC Chip Fabrication Fault SRAM Memory Resolution: sensor size, distance I. Introduction NANOSPIN-Meeting, , Kraków 5/27

6 Applications of High Sensitivity Sensors Mass Storage Hard Disk Drives Volume of nanobits I. Introduction NANOSPIN-Meeting, , Kraków 6/27

7 Applications of High Sensitivity Sensors Compass Sensing : 3D Magnetic Field I. Introduction NANOSPIN-Meeting, , Kraków 7/27

8 Applications of High Sensitivity Sensors Cars Sensing : Speed, Angle, Position Position Position Position Speed Position Position Position Position Speed Position Speed Angle Speed Position Distance I. Introduction NANOSPIN-Meeting, , Kraków 8/27

9 Applications of High Sensitivity Sensors Applications Requirements High sensitivity (nt-pt) Low nonlinearity and hysteresis (< 1%FS) Miniaturization (nanometer) Tunable resistance level ( -M ) Low power consumption Compatibility with technology (CMOS) Low cost I. Introduction NANOSPIN-Meeting, , Kraków 9/27

10 Properties of CoFeB/MgO/CoFeB Devices Scalability/Miniaturization (nanometer) Tunable resistance in wide range ( -M ) Compatibility with CMOS technology High TMR ( %, RT) 50x180 nm 2 Sony Resistance (k ) Ru(7nm) Ta(10nm) Co 40 Fe 40 B 20 (3nm) MgO(1.9 nm) Co 40 Fe 40 B 20 (2.5 nm) Ru(0.85 nm) Co 70 Fe 30 (2.5 nm) PtMn(20 nm) Ta(5 nm) SiO R L R H Magnetic field (mt) TMR (%) I. Introduction NANOSPIN-Meeting, , Kraków 10/27

11 CoFeB/MgO/CoFeB Devices Sensing problems Linearization of transfer curve Magnetic Noise II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 11/27

12 Sensing Problems Linearization of Transfer Curve Problem: High coercive field (Hc) R(kOhm) Known Methods External field Shape Anisotropy Exchange coupling H C Magnetic Field (Oe) Ineffective Complicated Expensive II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 12/27

13 Sensors Problems Linearization Problem: High coercivity Solutions: Thinning sensing layer and shape anisotropy 1 Perpendicular anisotropy 2 1.P. Wiśniowski, et al Effect of free layer thickness and shape anisotropy on the transfer curves of MgO magnetic tunnel junctions, J. Appl. Phys. 103, 07A910 (2008) 2. P. Wiśniowski, et al, Magnetic tunnel junctions based on out-of-plane anisotropy free and in-plane pinned layer structures for magnetic field sensors, IEEE Transaction on Magnetics, vol 48, no 11, (2012) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 13/27

14 Sensors Problems Linearization Thinning sensing layer and shape anisotropy Thing sensing layer Shape/Aspect Ratio Ta 5 Ru 5 CoFeB (t) MgO 1.35 CoFeB 3 Ru 0.9 CoFe 2.2 PtMn 18 Ta 30 Ru 18 Ta 5 glass CoFeB (t): 3 nm 1.45 nm Size h: 1.5 µm 4 µm W/h: 1-20 (aspect ratio) h M W H D Demagnetizing field H D = -N M N: demagnetization tensor Shape and size dependent 1P. Wiśniowski, et al Effect of free layer thickness and shape anisotropy on the transfer curves of MgO magnetic tunnel junctions, J. Appl. Phys. 103, 07A910 (2008) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 14/27

15 Sensors Problems Linearization TMR (%) Thinning Sensing Layer CoFeB: 30 Å CoFeB: 18 Å CoFeB: 17 Å 80 CoFeB: 15.5 Å CoFeB: 14.5 Å H 20 8x3 m 2 EA H (Oe) Critical thickness 1.55 nm TMR (%) Thinning Sensing Layer and Aspect Ratio 7.2%/Oe 7.7%/Oe 1.5x3 m 2 3x3 m H (Oe) EA Achieved Sensitivity 77 %/mt 1P. Wiśniowski, et al Effect of free layer thickness and shape anisotropy on the transfer curves of MgO magnetic tunnel junctions, J. Appl. Phys. 103, 07A910 (2008) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 15/27

16 Sensors Problems Linearization Perpendicular Anisotropy Sensing layer: Perpendicular anisotropy Reference layer: In-plane Anisotropy CoFeB MgO CoFeB M F Sensing Layer Reference Layer 2P. Wiśniowski, et al, Magnetic tunnel junctions based on out-of-plane anisotropy free and in-plane pinned layer structures for magnetic field sensors, IEEE Transaction on Magnetics, vol 48, no 11, (2012) 3P. Wiśniowski at al Magnetic field sensing characteristics of MgO based tunneling magnetoresistance devices with Co 40 Fe 40 B 20 and Co 60 Fe 20 B 20 electrodes, Sensors and Actuators A, 202, 64-68, (2013) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 16/27

17 Sensors Problems Linearization Perpendicular Anisotropy in Sensing Layer Effective Linearization Independent of shape and size ( m-nm) P. Wiśniowski, et al, Magnetic tunnel junctions based on out-of-plane anisotropy free and in-plane pinned layer structures for magnetic field sensors, IEEE Transaction on Magnetics, vol 48, no 11, 3840, (2012) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 17/27

18 Sensors Problems Linearization Perpendicular Anisotropy Different CoFeB Simple modification of sensing range 100mT- 0.1 mt Sensitivity 0.01 %/mt-0.90 %/mt 3 P. Wiśniowski et al Magnetic field sensing characteristics of MgO based tunneling magnetoresistance devices with Co40Fe40B20 and Co60Fe20B20 electrodes, Sensors and Actuators A, 202, 64, (2013) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 18/27

19 Sensors Problems Linearization Perpendicular Anisotropy Different CoFeB Nonlinearity Linear fits (Least Squares) to data and express as percentage of full scale (FS), which is normalized difference between the data and a linear fit Nonlinearity: 0.5 %FS do 2%FS Hysteresis: 1 %FS do 3%FS 3 P. Wiśniowski et al Magnetic field sensing characteristics of MgO based tunneling magnetoresistance devices with Co40Fe40B20 and Co60Fe20B20 electrodes, Sensors and Actuators A, 202, 64, (2013) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 19/27

20 Sensors Problems Magnetic Noise Field Sensitivity (FS) FS dr dh Field Noise (S fn ) I b ( V / T ) S fn 2 SV V / Hz) FS( V / T ) ( 2 ( T / Hz) Magnetic Noise Several orders of magnitude higher than electronic Increases with sensitivity II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 20/27

21 Sensors Problems Magnetic Noise 4Reduction of Noise by Thinning Sensing Layer Magnetic Noise Increase of magnetic noise with sensitivity 4P. Field Noise Reduction of field noise despite sensitivity increase Wiśniowski, et al Field noise in tunneling magnetoresistance sensors with different sensitivity, Applied Physics Letters, 106, , (2015) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, NANOSPIN-Meeting, , Kraków 21/27

22 Sensors Problems Magnetic Noise 6Reduction of Noise by Bias Voltage Magnetic Noise Field Noise 6P. Wiśniowski et al, Reduction of low frequency magnetic noise by voltage-induced magnetic anisotropy modulation in tunneling magnetoresistance sensors, Applied Physics Letters 105, , (2014) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, NANOSPIN-Meeting, , Kraków 22/27

23 Dynamic Properties 3dB Bandwidth vs MgO/RA 3 db vs MgO thickness 3 db vs RA Optimal RA=18 k m 2 High 3dB bandwidth Low R large Area High R small Area 7 M. Dabek, P. Wiśniowski, Effect of MgO thickness and bias voltage polarity on frequency response of tunneling magnetoresistance sensors with perpendicular anisotropy, Journal of Applied Physics, 117, 17A319, (2015) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 23/27

24 Dynamic properties Response to Current Pulse Response Time Response time: 11 ns Step response (% of SV) 100 Current pulse SV t rsp t rise Primary current FS=10V/T (+V b response) Time (ns) 8 M. Dabek, P. Wiśniowski, Dynamic response of tunneling magnetoresistance sensors to nanosecond current step, Sensors and Actuators A, (2015) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 24/27

25 Dynamic properties Response to Current Pulse Settling Time Step response (% of SV) t set(+vb) FS=10V/T Settling time: 137 ns SV Primary current FS=10V/T (+V b response) Settling margin (2% of SV) Cu rent pulse Time (ns) +/- 2% of SV 8 M. Dabek, P. Wiśniowski, Dynamic response of tunneling magnetoresistance sensors to nanosecond current step, Sensors and Actuators A, (2015) II.CoFeB/MgO/CoFeB Devices NANOSPIN-Meeting, , Kraków 25/27

26 Summary I.Introduction Applications of High Sensitivity Sensors Properties and Sensing Problems of CoFeB/MgO/CoFeB Devices II.CoFeB/MgO/CoFeB Devices Effective and Simple Solutions to Linearization Problems Tunable sensing range (100mT mt) High and tunable sensitivity ( %/mt) Reduction and control of magnetic noise by VCMA Suppression of noise bellow noise-sensitivity scaling Fast response to current step Response time (11 ns) Settling time (137 ns) NANOSPIN-Meeting, , Kraków 26/27

27 Acknowledgments EU Projects Ultrasmooth INESC Microsystems & Nanotechnology, Lisbon J. Almeida, J. Cao, S. Cardoso, A. Guedes and P.P. Freitas Partners: IBM Zurich, University Paris Sud, University of Leeds Spinswitch Siemens AG, Department of Innovative Electronics, Erlangen, Germany J. Ruhrig, J. Wecker and L. Bar Partners: IMEC Lueven, Spintec, UC London, University Paris Sud National Projects Magneto-electronics Devices for Detection and Sensing Low Magnetic Field Magnetic Tunnel Junctions for Sensing High Speed Magnetic Field Department of Electronics, AGH-UST Department of Electronics, AGH-UST T. Stobiecki, J. Kanak NANOSPIN-Meeting, , Kraków 27/27