Properties and Fabricating Technique

of Tunneling Magnetoresistance

Reporter : Kuo-Ming WuDay ： 2006/04/08

Outline

Development of Spintronics

Tunneling Magnetoresistance

Spin Torque Transfer

Conclusion

Development of Spintronics

Spin electronic ： Spintronics

The spin induced ferromagnetic phenomena has a large application valuation, and hence

builds on the Spintronics that the device working principle depends on the electron

spin direction.

Development of Spintronics

• The lower density of state of the spin-up than that of spin-down one at Fermi-level energy.

• The majority and minority spin electrons play important roles of the magneto-electric behaviors, such as magnetoresistance(MR).

Development of Spintronics

%100)(

)()(

21

21

orHHR

HRHRMR

The MR ratio is the variation of the sample resistance under different

magnetic field.

Development of Spintronics

Type Order FieldTemperatu

re

OMR 10-2% 1 T RT

AMR 2 % 10 Oe RT

GMR 5 % 10 Oe RT

CMR 106 % 5 T 100 KTMR 102 % 100~1 Oe RT

Tunneling Magnetoresistance

The energy band structure the 3d ferromagnetic materials near the Fermi level, such as Fe, Co, Ni

EF

Majority

Minority

n↑(EF) n↓(EF)%100)()(

)()(

FF

FF

EnEn

EnEnP

Tunneling Magnetoresistance

↑ ↑

Parallel-state SSLL

PG 2121

Tunneling Magnetoresistance

↑ ↓

AntiParallel-stateLSSL

APG 2121

Tunneling Magnetoresistance

LSSLAPG 2121

SSLLPG 2121

AP

APP

G

GGTMR

SL

SL

P11

111

SL

SL

P22

222

%1001

2

21

21

PP

PPTMR

M. Julliere Phys. Lett. A 54 225 (1975)

Tunneling Magnetoresistance

32

4

2

42

2

2

)exp(64

23

64

2)exp(

2

2

3VA

dh

mAe

dh

meAVA

dh

meJ

h

dmA

24

J. G. Simmons, J. Appl. Phys. 34,2581(1963)

Tunneling Magnetoresistance

-400 -200 0 200 400

-0.0010

-0.0005

0.0000

0.0005

0.0010

Mag

netiz

atio

n (E

MU

)

Magnetic Field(Oe)

→→

←←

→←

←→

-1000 -800 -600 -400 -200 0 200 400 600 800 1000-2

0

2

4

6

8

10

12

14

16

MR

ra

tio (

%)

Magnetic Field (Oe)

→→

←←

→←

←→

Ta 20/CoFe 25/AlOx 1.2/NiFe 30/Ta 40

Tunneling MagnetoresistanceTa 20/CoFe 25/AlOx 1.2 or 1.5/NiFe 30/Ta 40

-1.0 -0.5 0.0 0.5 1.0

-4.0x10-7

-2.0x10-7

0.0

2.0x10-7

4.0x10-7

J (A

mp/

um2 )

DC Bias(Voltage)

Simulator AlOx 1.2nm J-V

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-4.0x10-8

-2.0x10-8

0.0

2.0x10-8

4.0x10-8

J (A

mp/

um2 )

DC Bias (Voltage)

Simulator AlOx 1.5nm J-V

AlOx thickness

Barrier WidthBarrier Height

Inaccuracy

1.2 nm 1.126 nm 2.793 eV 0.255 %1.5 nm 1.482 nm 1.839 eV 0.290 %

-1000 -800 -600 -400 -200 0 200 400 600 800 1000

0

2

4

6

8

10

12

MR

Ra

tio (

%)

Magnetic Field (Oe)

Tunneling Magnetoresistance

-2000 -1000 0 1000 2000

-8.0x10-5

-6.0x10-5

-4.0x10-5

-2.0x10-5

0.0

2.0x10-5

4.0x10-5

6.0x10-5

8.0x10-5

Mag

netiz

atio

n (E

MU

)

Magnetic Field (Oe)

Ta 20/MnIr 12/CoFe 3/AlOx 1.2/CoFe 3 /NiFe 45/Ta 20

→→

←← →

←

←→

←←

→←

←→

→→

Spin Torque Transfer

0 100 200 300 400 500

0.00

0.05

0.10

0.15

0.20

Req

uirie

d C

urre

nt (

mA

)

Device Dimension (nm)

Field Induced Current Induced

Jc:5x106 A/cm2

→

←

Spin Torque Transfer

• In 1996, Slonczewski and Berger predicted that the magnetization of a magnetic layer can be reversed by injection of a spin polarized current and spin transfer to the layer.

• Magnetization reversal without application of an external magnetic field would be of considerable interest to switch magnetic microdevices.

Spin Torque TransferSlonczewski brought out that polarized spin current contribute torque is equal to:

eeff Ie

ssg

dt

dScScHs

dt

dS 21222

2 ˆˆˆ

Where γis the gyromagnetic ratio Heff is effect magnetic field c is the direction of symmetry axis of anisotropy αis the damping coefficient

1

23

213

4

ˆˆ314

P

ssPg

Spin Torque Transfer

Write to parallel

Spin Torque Transfer

Write to antiparallel

Spin Torque Transfer

SiO2/Ta 20nm/PtMn 15nm/CoFeB 3nm/Ru 0.8nm/CoFeB 3nm / AlOx 0.7 before oxide/CoFeB 2nm/Ta 40 nm

→

←

Spin Torque Transfer

Beam

holder

45° etching

hold

er

Beam

75° etching

holder

Beam

0° etching Redepositio

n

Spin Torque Transfer

Spin Torque Transfer

Spin Torque Transfer

Wafer

Coil

Source Chamber

ProcessChamber

ICP Power(13.56

MHz)

Bias Power(13.56

MHz) Coller

Inductively Coupled Plasma Reactive Ion Etching

Spin Torque Transfer

Spin Torque Transfer

500 x 250 nm

130 x 130 nm

Spin Torque Transfer

Spin Torque Transfer

Conclusion

• Spin torque transfer effect is more competent than field induced switching for TMR or GMR nano-devices.

• ICP-RIE etching procures higher taper angle and less damage than Ion Beam Etching for TMR fabrication process.

Thank YouFor

Your Attention