Challenges for integrated magnetoresistive sensors

P.P.Freitas, V. Martins, R.Ferreira, J.Gaspar, Elvira Paz, Jerome Borme ,Mariam Debs, Margaret Costa, Helder Rodrigues, Benito Rodriguez, Rumy Petrova, J.Piteira ( INL)

S.Cardoso, F.Cardoso, A.Rodrigues, Diana Leitao, R.Janeiro, J.P.Amaral, J.Germano, T.Costa, M.Piedade

(INESC MN)

E-mail: paulo.freitas@inl.int, pfreitas@inesc-mn.pt

Dublin , March 2012

Time (s)

fT to pT

pT

MCG

neuroelectronics

biochips

nT-µT

Magnetic Tunnel Junction sensorsBridge output

VOUT

Bottom Lead

Pinning Layer

Pinned LayerTunnel BarrierFree Layer

Top Lead

I

VBIAS

Linear range: tuneable : from 0.5mT to 100 mTMinimum field detectivity: nT Sensor size : few 100 nm2 to tens um2

Power comsumption: < 1mWTunable resistance: Ohm to 100’s kOhmsProcess compatibility: 200mm wafer process,

fully front end compatible

SPECS

-150 -100 -50 0 50 100 150

-600

-400

-200

0

200

400

600

Bridge Sensitivity : 26.7 mV/ mW /Oe

Bridge Sensitivity : 32.0 mV/ V /Oe

Bias Conditions :Voltage : 1000 mV Current : 0.300 mAPower : 0.3 mW

Bridge Output :Vmin : -532 mVVmax : +650 mVOutput Voltage : 1182 mV

Magnetic Response :Range (20-80%) : +29.40 OeHf : +2.39 [Oe]Hc : +4.15 [Oe]O

utpu

t Vol

tage

[mV]

External Magnetic Field [Oe]

Individual MTJ dimensions:5x70 m2

Magnetoresistive Sensors in AutomobilesApplications present in the Market

+ Navigation Systems + Electric Batteries Safety Systems+ Acceleration Sensors for Airbags (MEMS+Magnetoresistive)

Advantages:• Contactless, wear-free operating principle for angular and linear measurement• Large air gap• Large permissible air gap tolerances• Withstands extreme operating conditions• Full redundancy possible• Failsafe design• Flexible integration• High bandwidth for measurements in time slots of less than 100 ms

*Information from Sensitecwebsite

At least 15 different types of sensors using magnetoresistivedevices are already being integrated in automobiles!

2D Magnetometers/car navigation systemOutput from two orthogonal bridges

-314 -312 -310 -308 -306 -304 -302 -300 -298-320

-318

-316

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Offset Corrected XX Field Sensor Output [mV]

Offs

er C

orre

cted

YY

Fie

ld S

enso

r Out

put [

mV]

YY F

ield

Sen

sor O

utpu

t [m

V]

XX Field Sensor Output [mV]

VBridge=5V-8 -6 -4 -2 0 2 4 6 8

-8

-6

-4

-2

0

2

4

6

8

XX Component Sensor

YY Component Sensor

Sensor output during a 360○ rotation

INESC FP7 ENIAC demonstrator , CMOS integration underway

DNA targets

DNA probes

Substrate

Passivation

Magnetic labels

Spintronic transducer

Hybridization of DNA probe and target

1-Scalable magnetoresistive biochips for point of carediagnostics

Trends in Biotechnology, August 2004

Labelled targets

Hybridize firstLabel after

CF chip, Snip to Chip

INESC-MN’s static, multiplexed MR biochip8 mm 40 µm

Sensor

Spotted probe

ftmolar sensitivity (DNA chip)multiplexed analysisCMOS, microfluidics, sensors

10-1610-1510-1410-1310-1210-1110-10 10-9 10-8 10-7 10-6 10-5

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

No target DNA

V b

indi

ng

ac /

V s

enso

r

ac

DNA concentration (M)

Passive hybridization Assisted hybridization

Non-Complementarytarget DNA*

Tech review, Lab On Chip 2012

Cell detectionKg1a cells

cell=5-10m

Cells marked with 50nmFeOx particles

Lab on Chip (2011)

INESC MN Dynamic immunoassay platform

Scanning probescurrent imaging in Ics

100 1000 10000 100000

10

100

Noi

se (n

T/H

z0.5 )

Frequency (Hz)

INESC MN-NEOCERA

2x2 m2

Other applications:-Non destruct.test. (in alt to(ultrasound and inductive)-nanoparticle imaging systemsSPIN, 2011

Time (s)

MCG (Magneto Cardiography) neasurements with hybrid SC +SV sensor (CEA-Dublin)

Noise level 3-4 pT at 10 Hz, at 4 K

Towards < pT/sqrt(Hz) detectivity at 1 Hz, at RT: medical imaginig

0 20 40 60 80 1000

50

100

150

VThermal+VShot = 0.42 nV/Hz0.5SRS SIM910 Amplifier,40 dBSpan 100Hz; RBW 1Hz; AVG 1000

51 pT @ 30 Hz97 pT @ 10 Hz

Wafer#1650 (Singulus), RxA 150 m2

PME2, Sensor# 55A[m2] = 676(26x26) ; RLow= 1.36 Ro = 2.1 ; TMR = 97%; S = 72 %/Oe

Sv[

pT/H

z0.5 ]

f[Hz]

RoomTemperature

ExternalLong Bias 35 Oe

IBias [A] 0.01 0.1

(1pT at 500 kHz, RT) Hybrid flux guide + TMR sensor

APL,2008

pT DC Magnetic Field DetectionHybrid SpinMEMS; DC to AC flux transformer

2006-2010, hybrid MR /thin film MEMS

1 nT at 1 Hz

2x6um2

SV sensordc flux

gate

ac flux

2012INESC MNINLUC Berkeley

Stimulation electrode

Recording electrode

Rat hippocampus

Synaptic current monitoring with highSpatial resolution ( with A.Sebastiao, IMM)

108200 108300 108400 108500 108600 108700 108800

-2,0x10-5

-1,0x10-5

0,0

1,0x10-5

2,0x10-5

3,0x10-5

4,0x10-5

Volta

ge (V

)Time (ms)

svon_Pump_Krebs_after1h30min_Oxigen__stimulation_30_100

MEMSMRCMOS

Remote sensor networks: RF antenna-MR sensor microsystem( large bandwidth)

APL, 2011

2mm antenna

SV