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Properties and Fabricating Technique
of Tunneling Magnetoresistance
Reporter : Kuo-Ming WuDay : 2006/04/08
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Outline
Development of Spintronics
Tunneling Magnetoresistance
Spin Torque Transfer
Conclusion
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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.
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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).
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Development of Spintronics
%100)(
)()(
21
21
orHHR
HRHRMR
The MR ratio is the variation of the sample resistance under different
magnetic field.
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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
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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
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Tunneling Magnetoresistance
↑ ↑
Parallel-state SSLL
PG 2121
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Tunneling Magnetoresistance
↑ ↓
AntiParallel-stateLSSL
APG 2121
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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)
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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)
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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
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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 %
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-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
→→
←← →
←
←→
←←
→←
←→
→→
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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
→
←
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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.
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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
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Spin Torque Transfer
Write to parallel
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Spin Torque Transfer
Write to antiparallel
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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
→
←
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Spin Torque Transfer
Beam
holder
45° etching
hold
er
Beam
75° etching
holder
Beam
0° etching Redepositio
n
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Spin Torque Transfer
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Spin Torque Transfer
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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
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Spin Torque Transfer
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Spin Torque Transfer
500 x 250 nm
130 x 130 nm
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Spin Torque Transfer
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Spin Torque Transfer
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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.
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Thank YouFor
Your Attention