T.Stobiecki Katedra Elektroniki AGH Magnetic Tunnel Junction (MTJ) or Tunnel Magnetoresistance (TMR) or Junction Magneto- Resistance (JMR) 11 wykład 13.12.2004
T.Stobiecki Katedra Elektroniki AGH
Magnetic Tunnel Junction (MTJ)or
Tunnel Magnetoresistance (TMR)or
Junction Magneto- Resistance (JMR)
11 wykład 13.12.2004
Spin Polarization, Density of States
Ferromagnetic metal (Fe)
nn
nnP
Spin Polarization Density of states 3d
Ni 33 %
Co 42 %
Fe 45 %
Ni80 Fe20 48 %
Co84 Fe16 55 %
CoFeB 60%
Material Polarizations
Normal metal (Cu)
E F
M a jor ity Sp in M ino rity Spin
E
DOS
nn
)()( FF EnEn )()( FF EnEn
N
E F
M a jo rity Sp in M ino rity Sp in
E
DOS
nn
Tunneling in FM/I/FM junction
II
III
nn
nnP
IIII
IIIIII
nn
nnP
III
III
M
MM
PP
PP
I
IITMR
1
2
R
RRTMR
IIIIIIM
nnnnI
IIIIIIM
nnnnI
II
I I
FM I (PI) FM II (PII)
Barrier
eV N
E F
M a jo rity Sp in M ino rity Sp in
E
DOS
nn
N
E F
M a jo rity Sp in M ino rity Sp in
E
DOS
nn
E F
M a jori ty Sp in M ino rity Spin
E
DOS
Nnn
Type of MTJs
Standard junction
FM
I
FM
FM
I
FM
I
FM
Spin valve junction(SV- MTJ)
Double barrier junction
B
AF
FM
I
FM
Application-Oriented Properties of S-V MTJ
• Tunnel Magnetoresistance -TMR
• Resistance area product -RxA
• Interlayer coupling field HS
• Exchange bias field HEXB
• Coercive field pinned HCP
and free HCF layer
• Switching field HSF
Magnetic
Materials
• I (Al-O,MgO..)
• FM (Co, CoFe, NiFe)
• AF (MnIr, PtMn, NiO)
• Buffer (Ta,Cu, NiFe)
Treatment
• Annealing
• Field cooling
Preparation
• Sputtering deposition
• Oxidation
SV-MTJ
Electric
Magnetic and Electric Parameters
B
AF
FM II (Pinned)
I
FM I (Free)Interlayer coupling
HSExchange coupling
HEXB
HSF switching fields
HS
HEXBHCP
HCF
HSF
R
RRTMR
Applications of SV-MTJ
M-RAM
SPIN-LOGIC READ HEADS
SENSORS
SV-MTJ
SV-MTJ Based MRAM
Bit lines
Word lines
IB
IW
Writing “0”
Writing “1”
IB
Memory Cell
Reading current IR
Memory Matrix
SV-MTJ
IW
Writing - rotation of the free layer
Reading - detection of a resistance of a junction
SV- MTJ as MRAM component must fulfill requirements - Thermal stability- Magnetic stability - Single domain like switching behaviour- Reproducibility of RxA, TMR and Asteroids
Hy/
H(0
)
1
-1
-1 10
0
Critical switching fields Hx , Hy (S-W) asteroid
Motorola: S.Tehrani et al. PROCEEDINGS OF THE IEEE, VOL. 91, NO. 5, MAY 2003
Features of M-RAM - Non-volatility of FLASH with fast programming, no program endurance limitation
- Density competitive with DRAM, with no refresh
- Speed competitive with SRAM
- Nondestructive read
- Resistance to ionization radiation
- Low power consumption (current pulses)
• Single 3.3 V power supply
• Commercial temperature range (0°C to 70°C)
• Symmetrical high-speed read and write with fast access time (15, 20 or 25 ns)
• Flexible data bus control — 8 bit or 16 bit access
• Equal address and chip-enable access times
• All inputs and outputs are transistor-transistor logic (TTL) compatible
• Full nonvolatile operation with 10 years minimum data retention
Motorola: S.Tehrani et al. PROCEEDINGS OF THE IEEE, VOL. 91, NO. 5, MAY 2003
SV-MTJ Based Spin Logic Gates
Siemens & Univ. Bielefeld: R. Richter et al. J. Magn.Magn. Mat. 240 (2002) 127–129
SV- MTJ as spin logic gates must fulfill requirements - Thermal stability- Magnetic stability - Centered minor loop- Single domain like switching behaviour- Reproducibility of R, TMR
RMTJ2
Logic Inputs
Logic Output
Programing Inputs
SV-MTJs
RMTJ3
RMTJ1
RMTJ4
(+, ) IB
(+, ) IA
IS
ISVO UT
VOUT= IS(RMTJ3 + RMTJ3 – RMTJ1 – RMTJ2)
Logic Inputs MTJ 3, MTJ 4
0
2 VOUT
(0,0) (1,1)(1,0)(0,1) (0,0) (1,1)(1,0)(0,1)
MTJ 1 MTJ 2 MTJ 1 MTJ 2
NAND NOR
„1"
„0"
Lo
gic
Ou
tpu
t
-2 VOUT
Features of Spin Logic Gates
- Programmable logic functions (reconfigurable computing)
- Non-volatile logic inputs and outputs
- Fast operation (up to 5 GHz)
- Low power consumption
- Compatibility to M-RAM
SV-MTJ Based Read Heads
SV-MTJ as a read sensor for high density (> 100Gb/in2) must fulfill requirements - Resistance area product (RxA) < 6 -m2 - High TMR at low RxA
Experiments on SV -MTJsA MTJs
3 6 10 30 50
Substrate Si (100)
Cu 25 nm
MnIr 12 nm
CoFe t nm
Al2O3 1.4 nm
NiFe 3 nm
Ta 5 nm
Cu 30 nm
Ta 3 nm
Au 25 nm
0 10 30 60 100
Substrate Si (100)
SiO2
Ta 5 nm
Cu 10 nm
Ta 5 nm
NiFe 2 nm
Cu 5 nm
MnIr 10 nm
CoFe 2.5 nm
Al2O3 1.4 nm
CoFe 2.5 nm
NiFe x nm
Ta 5 nm
B MTJs
A structure prof. G. Reiss laboratory University BielefeldB structure prof. T. Takahasi laboratory, Tohoku University
10 mm
Junction
Junction
Junctions size (180180) m2
Effect of Annealing on TMRAs deposited Annealed
-150 -100 -50 0 50 100 1500
2
4
6
8
10
12
14
TMR = 13.4 %
TM
R [%
]
H [kA/m]
100 150 200 250 300 3500
5
10
15
20
25
30
35
40
TM
R [%
]
Annealing temperature (oC)
100 nm (10 sec) 100 nm (13 sec) 100 nm (16 sec) 10 nm (10 sec) 10 nm (13 sec) 10 nm (16 sec)
-120 -80 -40 0 40 80 1200
10
20
30
40
50
TMR = 48 %
TM
R [%
]
H [kA/m]
10 mm
H=80 kA/m
annealing 1 hour in vacuum 10-6 hPa
Interlayer and Exchange Coupling Fields
A MTJs B MTJsExchange coupling fields Interlayer coupling fields
-100 -75 -50 -25 0 25 50-3
-2
-1
0
1
2
3
Ke
rr r
ota
tion
[min
]
H [kA/m]
3nm 6nm 10nm 30nm 50nm
-3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Ke
rr r
ota
tion
[min
]
H [A/m]
10 nm 30 nm 60 nm 100 nm
-100 -75 -50 -25 0 25 500
10
20
30
40
50
3nm 6nm 10nm 30nm 50nm
TM
R [
%]
H [Oe]
-3000 -2000 -1000 0 1000 2000 3000
0
10
20
30
40
TM
R[%
]
H [Oe]
10 nm 100 nm
Interlayer and Exchange Coupling Fields
FFS tM
JsH
0
PP
EXBEXB tM
JH
0
Temperature Dependence of TMR
)()()( TGTGTdG APP
AP
APP
G
GGTMR
P. Wiśniowski, M.Rams,... Temperature dependence of tunnel magnetoresistance of IrMn based MTJ, phys. stat. sol (2004)
-40 -30 -20 -10 0 10 20
0
10
20
30
40
50
30K 50K 70K100K150K200K250K300K
TM
R [
%]
H [Oe]
t=10nm (3000 C)
-20 -15 -10 -5 0 5 10 15 200
10
20
30
40
50
60t=100nm (2700 C)
TM
R[%
]
H [Oe]
30k 50k 70k 100k 150k 200k 250k 300k
Total Conductance
)()]()(1)[()( 21 TGTPTPTGTG SITAP )()]()(1)[()( 21 TGTPTPTGTG SITP
)()()(2)()()( 21 TPTPTGTGTGTdG TAPP
)sin(/)( 0 CTCTGTGT )1()1()()( 2/3202
2/310121 TbPTbPTPTP
Varies slightly with T Varies with T as magnetization does Bloch law
Negligible
Dominant
)()]cos()()(1)[(),,( 212121 TGTPTPTGTG SIT
AP
APP
G
GGTMR
Polarization, Bloch Law )()()(2)( 21 TPTPTGTdG T
][102.9[%]45
][100.1[%]482/36
202
2/36101
KbP
KbP100 nm
AP
P
1. Set H= – 2000 Oe
2. Cooling H= 500 Oe
3. Measured M (T)1. Set H= – 2000 Oe
2. Cooling H= –500 Oe
3. Measured M (T)
)1()( 2/30 BTMTM
][1099.6
][1076.62/36
2/36
KB
KB
Spin Independent ConductanceTAPPSI GGGG 2/)(
NTGSI
66.1
][1021.3 6
SKN
33.1
][100.2 6
SKN
Hopping conductance, low level of defects
Hopping conductance, high level of defects
TIMARIS: Tool status
Tool #1 – process optimization on 200 mm wafers since mid of March 03
Tool #2 – The Worlds 1st 300 mm MRAM System is Ready for Process in August 03
Multi (10) Target Module
Oxidation / Pre-clean Module
Transport Module
Clean room
Sputtering System
Metal depo.
Plasma Oxidation
LL 1 : wafer-in
LL 2 : Bridge Reactive
sputter : surface smooth
Measurements R-VSMMOKE
Sample
H coilsy
H coilsx
MOKE with Orthogonal Coils