Nanourządzenia elektroniki...

XLII Zjazd Fizyków Polskich, Nanotechnologia, Poznań, 12.09.2013 1/53

Katedra Elektroniki, Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

T. Stobiecki

Department of Electronics AGH, Poland

Nanourządzenia elektroniki spinowej

NANOSPIN - Nanoscale spin torque devices for spin electronics

W. Skowroński, M. Czapkiewicz, M. Frankowski, J. Kanak, P. Mietniowski, W.

Powroźnik, Z. Szklarski, P. Wiśniowski, J. Wrona (Singulus A.G), A. Żywczak

E – Control – Urządzenia elektroniki spinowej sterowane polem

elektrycznym



Magnetic Recording

and Magnetic Sensors

Semiconductor Devices

and Integrated Curcuits

CHARGE SPIN

NANOELECTRONICS

Metal

SpintronicsMRAM + Circuit Technology

Semiconductor

Spintronics

SPINTRONICS



Spintronics road map

Commercial spintronics devices• head TMR/HDD

• M-RAM, STT-RAM

Technology of magnetic nanostructers (TMR-MTJ)• sputtering

• nanofabrication (e-litography)

Spin Transfer Torque

• Current Induced Magnetization Switching (CIMS) STT-RAM

• spin dynamics: ST-FMR ST- Oscillator

Voltage-induced magnetism

• Static anisotropy changes – tunable sensor

• voltage induced precession

Conclusions

Plan

Zielona informatyka Green I T(echnology)



Green I(nformation)T(echnology)

S. Yuasa (2012)

`



Green IT

S. Yuasa (2012)

Tomasz Stobiecki, Aalto University, August 2013 7/35

Department of Electronics, AGH University of Science and Technology

S. Yuasa talk , Kraków Jan (2012)

Green IT



Green IT

S. Yuasa (2012)



Magnetoresistance

MR ratio (RT & low H)

AMR effect

MR = 1~2%

Year

1857

1990

1995

2000

2005

2013

Lord Kelvin

TMR effect

MR = 20~70%

1985GMR effect

MR = 5~15%

T. Miyazaki, J. Moodera J. Slonczewski, L. Berger1996

Device applications

HDD head

Inductive

head

MR head

GMR head

TMR head MRAM

Memory

Giant TMR effect

MR = 200~1000%

MgO -TMR headSpin Torque

MRAM Microwave, E-control.

Novel

devices

1967

A. Fert, P. Grünberg, J. Barnaś



Tunneling – Julliere’s model

Ferromagnetic-electrode 1 Ferromagnetic-electrode 2Insulator


XLII Zjazd Fizyków Polskich, Nanotechnologia, Poznań, 12.09.2013

Magnetic field switching

TMR = 175%

10/53



TMR = 175%

Curent Induced Magnetization Switching - CIMS

11/53



(001)MgO

FFT

Technology of magnetic nanostructers (TMR)

TEM EDX

L. Yiao, S. van Dijken

0.9nm

12/53



P. Wisniowski, T.Stobiecki J. Appl. Phys. 100 (2006) 013906

J. Kanak, T.Stobiecki Vacuum 82 (2008)1057

TMR race

13/53



0 5 10 15 20 25 30 35 400

1000

2000

3000

4000

IrMn(111)

a

b

Inte

nsity [

co

un

ts/s

ec]

[deg]

0

100

a) RMS = 0.3 nm b) RMS = 0.6 nm

buffer

IrMn

Ta

20

40

60

80a2_m - IrMn[111]

20

40

60

80b2_m - IrMn[111]

a) b)AFM

XRD – rocking curve

XRD – pole figure

Barrier quality

15/53



Sputtering system



0

50

100

150

200

250

0,1 1,0 10,0 100,0 1 000,0 10 000,0

RA [ µm²]

TM

R [

%]

nat ox CAPRES

nat ox patterned

plasma ox CAPRES

plasma ox patterned

Freescale MgO_4

Anelva2006 (MgO+Mg)

Anelva2006 (MgO)

TDK2006

MgO - TMR vs. RA

H. Maehara et al. Applied Physics Express 4 (2011) 033002

J. Wrona, T.Stobiecki, et al. JPC (2010)

17/53



Courtesy of

Singulus TIMARISMulti Target Module

Top: Target Drum with 10

rectangular cathodes; Drum

design ensures easy

maintenance;

Bottom: Main part of the

chamber containing LDD

equipment

Oxidation ModuleLow Energy Remote

Atomic Plasma Oxidation;

Natural Oxidation;

Soft Energy Surface

Treatment

Transport Module

(UHV wafer handler)

Soft-Etch Module

(PreClean, Surface

Treatment)

Cassette Module

(according to

Customer request)

Ultra – High – Vacuum Design: Base Pressure 5*10-9 Torr (Deposition Chamber)

High Throughput (e.g. MRAM): 9 Wafer/Hour (1 Depo-Module)

High Effective Up-time: 18 Wafer/Hour (2 Depo-Module)

Sputtering deposition (industrial process)



Magnet Array

Sputter Target

Wafer

Linear Dynamic Deposition (LDD)

•Leakage field of cathode parallel to wafer travel direction:

Ideal symmetry for magnetic film applications

•Stationary Aligning Magnetic Field (AMF):

AMF can be optimized with cathode

SN

Yoke Yoke

Target Drum Targets

Wafer Travel

Deposition Area

•Short Target-Substrate Distance:

Good thickness uniformity and coating efficiency

•Thickness adjusted by wafer speed:

Precisely control & repeatability

Advantages:

Courtesy of

19/53



Wedge technology

position of the wafer

wafer velocity

start velocity

deposition area

constant velocity gradient

J. Wrona et al. Low resistance magnetic tunnel junctions with MgO wedge barrier, ICM 2009.

Sputter Target

Wafer

• base pressure: p0 510-9 mTorr

• MgO - 4kW, rf magnetron sputtering,

variable Ar pressure 1 – 15 mTorr

• CuN – 4 kW, reactive (Ar+N) magnetron dc

•Ta,Ru,CoFeB – 1.5 kW magnetron dc

20/53



• MTJ stack deposited in Singulus

• MgO wedge thickness: 0.6 nm up to 1nm

(slope 0.017 nm/cm)

Multilayer stack

Co70Fe30 2 PL

Ru 0.9

Co40Fe40B20 2.3 RL

wedge MgO

Co40Fe40B20 2.3 FL

IC

SAF

EB

Ta 10

CuN 30

Ru 7

ca

pp

in

g

Si/SiO2

Ta 5

CuN 50

Ta 3

CuN 50

Ta 3

PtMn 16 AF

buffer

Wafer characterization: microstructure/texture – XRD, AFM

• electrical, magnetic: TMR, RA, MOKE and VSM-loops

Nanopillars

• 3 step e-beam lithography, ion etching, lift-off

SiO substrate2

Ta

Ta

CuN

CuN

wedge MgO

Co Fe 270 30

Ru 0.9

Co Fe B 2.340 40 20

PtMn 16

Ta 10

Al O2 3

CuN 30

Au

5

3

50

50

CoFe 30

V+

V-

Ta 3

Co Fe B 2.340 40 20

Ru 7

21/53



0.6 0.7 0.8 0.9 1.0

10

100

0.5

5

MgO thickness (nm)

RA

(O

hm

m2)

T

MR

(%

)

TMR

RA

exponential fit

a)

A. Zaleski, W. Skowroński, T.Stobiecki, et al. JAP (2012)

TMR & RA vs. MgO thickness



Nano-e-beam lithography

-1.0 -0.5 0.0 0.5 1.0

100

150

200

250

300

Resis

tance [O

hm

]

Voltage [V]

Nanopillars 3 step e-beam lithography, ion etching, lift-off

e-lithography by RAITH system



TMR = 175%

Curent Induced Magnetization Switching - CIMS

24/53



Spin Transfer Torque (STT)

Unpolarized

electrons

Polarized

electrons

Transmitted

electrons

Polarizer P Free layer M

Local magnetizationConduction Electrons Transfer of transverse

moment m

=

Torque

(Spin Torque ST)

ST tends to align M (anti-)parallel to P

Electron

flow



dt

dmmHm

dt

dmeff

Magnetization dynamics LLG

precession damping

L(andau) L(ifszic) G(ilbert) dynamics

26/53



dt

dmmHm

dt

dmeff Mm

VolMMmm

VolM SS

)(||

precession dampingSTT

Spin Transfer Torque (STT)

27/53



STT – CIMSSpin Transfer Torque Curent Induced Magnetization Switching

I = ICritical

28/53



-1.0 -0.5 0.0 0.5 1.0

-2

-1

0

1

2 1 nm MgO

0.9 nm MgO

(1

0-19 N

m)

I (mA)

-1.0 -0.5 0.0 0.5 1.0

-2

-1

0

1

2

(

10-1

9 Nm

)

I (mA)

experiment theory

W.Skowroński, T.Stobiecki et al. PRB 87, 094419 (2013)

STT components

29/53



Micromagnetic switching (OOMMF)

I= 7 mA, P=0.7 α=0.01 M. Czapkiewicz



-2000 -1000 0 1000 2000160

200

240

280

320

360

TMR = 100%

RA= 3.5 m2

Angle 60°

Re

sis

tan

ce [

Oh

m]

Field [Oe]

Bias tee

GHz generator

+ AM

Voltage/current

sourcemeter

Lock-in

amplifier

Ref

8kHz

Freq sweep

2 – 10 GHz

Measurement setup for spin dynamics

•MTJ sample placed in the magnetic field and tilted by a certain degree

•Amplitude modulated RF signal supplied to the MTJ through a bias tee

•Small DC signal measured using lock-in detection

31/53



130 nm

230 nm

leads 50

Nanopillar with coplanar wave guide

32/53



ST-FMR oscillations

• MTJ supplied with a RF signal

• Generates DC voltage at tunable

resonant frequency

• Inverse effect applicable as

microwave generator

3 4 5 6 7

0

5

10

15

20

Vm

ix (

V)

Frequency (GHz)

External magnetic

field (Oe)

250

300

350

400

450

500

550

600

650

700

750

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.50

2

4

6

8

10

12

FL AP

FL P

Kittel formula fit

Fre

qu

ency

(G

Hz)

Field (kOe)

W.Skowrońsk, T.Stobiecki et al. PRB 87, 094419 (2013)

Bias tee

GHz generator

+ AM

Voltage/current

sourcemeter

Lock-in

amplifier

Ref

8kHz

Freq sweep

2 – 10 GHz



2

2

2

4

1RFmix I

I

VV

ASI

VoleMI

VRF

S

||

sin 22

42

1

dV

dT

dI

dVe ||

|| sin2

dV

dT

dI

dVe sin

2

Wang et al. PRB 79, 224416, 2009

6 7 8 9

-10

0

10

0 .25 V

0.1 V

0 V

-0.1 V

-0.25 V

V m

ix (

uV

)

Frequency (GHz)

6 7 8 9-8

-4

0

4

8

12

0.1 V

S + A fit

S

A

V m

ix (

uV

)

Frequency (GHz)

Torkances and torques

•Vmix is derived from the LLGS equation

•S and A are symmetric and asymmetric

lorentzians:

34/53



Torque (STT) components

W.Skowroński, T.Stobiecki, S. Van Dijken et al. PRB 87, 094419 (2013)

in plane componentOut of plane component

35/53



-1.0 -0.5 0.0 0.5 1.0

-2

-1

0

1

2

(

10-1

9 Nm

)

I (mA)

experiment theory

W.Skowroński, T.Stobiecki, S. Van Dijken et al. PRB 87, 094419 (2013)

STT components

Ab initio band calcultions

Heiliger, Stiles PRL 100, 186805, 2008

36/53



Measurement setup for spin dynamics

W. Skowroński

37/53



STT – CIMSSpin Transfer Torque Curent Induced Magnetization Switching

I = ICritical

1,0 1,5 2,0 2,5

2

4

6

8

10

Pow

er

(nV

/Hz

0.5)

Frequency (GHz)

DC current

-0.1 mA

-0.5 mA

-1 mA

-1.5 mA

-1.7 mA

-1.8 mA

W.Skowroński, T.Stobiecki, S. van Dijkenet al. APEX 5, 063005 (2012)

38/53



Zero-magnetic field STO

• Use of:– Perpendicular anisotropy of thin CoFeB on MgO

– Ferromagnetic coupling between FL and RL (0.9 nm MgO)

• In-plane STT-induced oscillations

W.Skowroński, T.Stobiecki, S.Van Dijken et al. APEX 5, 063005 (2012)



Deriving the critical current

J- current density (A/m2)

S-Area (m2)

e- electron charge (A*s)

ħ– Planck constant (J*s)

0Ms – Magnetization (T)

Hk- Anisotropy field (A/m)

V- Volume (m3)

Dimension less

efficiency factor Dimension less

energy loss rate

Energy of free layer

Available energy

energyVHM volumeKS

2

0

e

JSenergy

surface

40/53

220

2volumeSeffeffective VMH

e

Ip



35 ± 1136 ± 7

P APAP PStability factor

exp2

Tk

VMH

B

SC

302

CalcB

SC

Tk

VMH

-1.0 -0.5 0.0 0.5 1.0

400

600

800

1000

P P

AP 1 ms

2.7 ms

7.3 ms

19.8 ms

53.7 ms

b)

R

esis

tan

ce (

Oh

m)

Voltage (V)

AP

-20

-15

-10

-5

0

5

10

15

200 2 4 6 8 10 12 14 16 18

ln (tp/t

0)

Jc

+ AP to P

Jc - P to AP

Jc (

MA

/cm

2)

0

0 ln2

1τ

τ

VMH

TkJJ P

SC

Bcc

• results of MTJ with 0.96 nm thick MgO barrier

• Jc0 estimation

CIMS – critical current Jc0

W.Skowroński, T.Stobiecki et al. JAP 107, 093917 (2010)

41/53



0 5 10 15 20 25-5.5

-5.0

-4.5

-4.0

-3.5

JC (

MA

/cm

2)

ln(P/

0)

JC0

= -5,27 MA/cm2

JC = J

C0[1-(k

BT/E)ln(

p/

0)]

10-9

10-7

10-5

10-3

10-1

101

P (s)

0 4 8 12 16 20-20

-15

-10

-5

0

5

10 Jc AP ->P

Jc (

MA

/cm

2)

ln (tp/t

0)

JC P -> AP

effS

B

C VHMe

I

0

Critical current

4eff a SH H M

M out of plane

2eff a SH H M M in plane

M out of plane

M in plane

Perpendicular magnetisation reduces the critical switching current!

In our case 3 times!

M in plane

CoFeB/MgO/CoFeB with perpendicular

magnetic anisotropy PMA

42/53



Everspin officially announces the world's first ST-MRAM chip,

will be available in 2013

A couple of days ago we reported that Everspin will start sampling

ST-MRAM chips soon, and today we got official word from Everspin

that they are now sampling the first ST-MRAM chip. The

EMD3D064M is a 64Mb DDR3 device, and select customers are

already evaluation samples. Everspin is currently targeting the

enterprise SSD market, to complement flash memory.

45/53



HDD- head

J. Kanak

MFM



Voltage-tunable magnetic field sensor

• CoFeB/MgO based MTJ field sensor

• Bias voltage changes the perpendicular magnetic anisotropy

• Thin CoFeB layer

• Thick MgO (1.35 nm) – no STT present

W.Skowroński, P.Wiśniowski et al. APL 101, 192401, 2012



Voltage-induced dynamics

• MTJ with thick MgO (2nm) – high resistance, low current

• Voltage-induced FMR precession in MTJ

• Bias voltage affect magnetic anisotropy – change in the resonance

frequencyW. Skowroński, T. Stobiecki et al. MMM2013

-300 -200 -100 0 100 200

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d T

MR

Field (Oe)

Bias voltage (V)

0.01

0.6

-0.6

1.0 1.5 2.0 2.5

-0.2

-0.1

0.0

0.1

0.2 -1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Voltag

e (

mV

)Frequency (GHz)

Bias voltage (V):



MRAM example

Existing MRAM – up to 64 MB capacity CMOS technology

Obstacle – critical current density

)

Toshiba, ISSCC conference (2010)



Conclusions

• Successful fabrication of MTJ nanopillars with a

ultrathin MgO barrier

• Spin Transfer Torque (STT) effect in MTJs was

quantitavely analysed

• Current Induced Magnetization Switching (CIMS) and

and ST- oscillations in nanopillars were demonstrated

• Voltage-Induced magnetic anisotropy – tunable sensor

and RF-signal detection were demonstrated



AcknowledgementsAGH Department of Electronics

M. Czapkiewicz (simulations)

J. Kanak (structure)

W. Skowronski (e-lithography Uni Bielefeld, TMR, CIMS, Spin-diode,)

J. Wrona (deposition in Singulus, CIPT-capres measurements)

IMP PAS

J. Dubowik

H. Głowiński

AMU Poznań

J. Barnaś (theory)

P. Balaz

P. Ogrodnik

EPFL

Jean-Philippe Ansermet

A. Vetro

Singulus AG

J. Langer

B. Ocker

W. Maass

University of Bielefeld

K. Rott (e-lithography training for WS)

G. Reiss,

Aalto University, Espoo, Finland

S. van Dijken



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