Spin Torque Transfer Technology

1
Spin Torque Transfer Technology
S. James Allen UC Santa Barbara

• Science
• Technology
• Spin Torque Transfer RAM, STT-RAM
• Spin Torque Transfer Nano-oscillators
• Spin logic devices

2
Spin Torque Transfer Technology
With input from
Mark Rodwell UC Santa Barbara Bob
Buhrman Cornell Stu Wolf U. Virginia H.
Ohno Tohoku University Nick Rizzo Free
Scale Yiming Huai Grandis Bill
Rippard NIST Steve Russek NIST Eli
Yablonovitch UC Berkeley Ajey Jacob Intel
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Spin Torque Transfer Technology
From R. A. Buhrman, Spin Torque Effects in
Magnetic Nanostructures, Spintech IV, 2007

• Science
• Technology
• Spin Torque Transfer RAM, STT-RAM
• Spin Torque Transfer Nano-oscillators
• Spin logic devices

4
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).

• Heisenberg exchange
• Giant magneto resistance
• Spin transfer torque

5
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Non-magnetic
Ef , 1-band
Ferromagnet
Ferromagnet

• Heisenberg exchange
• Giant magneto resistance
• Spin transfer torque

6
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Ef , 1-band
Ferromagnet
Ferromagnet
Ferromagnetic
Ferromagnetic
Anti-ferromagnetic
Anti-ferromagnetic

• Heisenberg exchange

7
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Ef , 1-band
P 1, ideal, perfect spin valve

• Giant magneto resistance

8
H. Ohno, Spintronics

Seminar, UCSB May, 2008
9
H. Ohno, Spintronics

Seminar, UCSB May, 2008
P 1, ideal, perfect spin valve
10
H. Ohno, Spintronics

Seminar, UCSB May, 2008
M. Hosomi, et al., A novel nonvolatile memory
with spin torque transfer magnetization
switching spin-ram, Electron Devices
Meeting,2005. IEDM Technical Digest. IEEE
International, pp. 459-462.
Free
Fixed SyF
P 1, ideal, perfect spin valve
11
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
q
Free

• Spin transfer torque

12
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Fixed
q
Free

• Spin transfer torque

13
Spin Torque Transfer Science
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Fixed
q
Free

• Spin transfer torque

14
Spin Torque Transfer Technology
From R. A. Buhrman, Spin Torque Effects in
Magnetic Nanostructures, Spintech IV, 2007

• Science
• Technology
• Spin Torque Transfer RAM, STT-RAM
• Spin Torque Transfer Nano-oscillators
• Spin logic devices

15
GMR and STT --- STT-RAM
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Fixed
q
Free

• Spin transfer torque

16
GMR and STT --- STT-RAM
T. Kawahara, R. Takemura, K. Miura, J. Hayakawa,
S. Ikeda, Y.M. Lee, R. Sasaki, Y. Gotot, K. Ito,
T. Meguro, F. Matskura, H. Takahash, H. Matsuoka
and H. Ohno, 2 Mb SPRAM (Spin-Transfer Torque
RAM) with bit-by-bit bi-directional current write
and parallelizing-direction current read, IEEE J
Solid-State Circuits, 43, 109 (2008).
200 mA
17
Conventional MRAM (toggle) and Spin Torque MRAM
Spin polarized current produces torque to
reverse free layer.
H field produces torque to reverse free layer.

• Need Isw 40 mA/bit for 0.4 um x 1.0 um.
• Isw constant for smaller bits.

• Isw lt 1 mA/bit for 0.06 mm x 0.12 mm bit.
• Isw reduces as bit scales smaller.

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STT-RAM 2005
Free
Fixed SyF
M. Hosomi, H. Yamagishi, T. Yamamoto, K. Bessho,
Y. Higo, K. Yamane, H. Yamada, M. Shoji, H.
Hachino, C. Fukumoto, H. Nagao, H. Kano, A novel
nonvolatile memory with spin torque transfer
magnetization switching spin-ram, Electron
Devices Meeting,2005. IEDM Technical Digest. IEEE
International, pp. 459-462.
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STT-RAM 2005
M. Hosomi, H. Yamagishi, T. Yamamoto, K. Bessho,
Y. Higo, K. Yamane, H. Yamada, M. Shoji, H.
Hachino, C. Fukumoto, H. Nagao, H. Kano, A novel
nonvolatile memory with spin torque transfer
magnetization switching spin-ram, Electron
Devices Meeting,2005. IEDM Technical Digest. IEEE
International, pp. 459-462.
CMOS driver 100 mA/100 nm
S. Ikeda, J.Hayakawa, Y.M. Lee, F. Matsukura, Y.
Ohno, T. Hanyu and H. Ohno, Magnetic tunnel
junctions for spintronic memories and beyond,
IEEE Trans Elec. Dev. 54, 991 (2007).
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STT-RAM 2005
Read 0.2 V lt write!
M. Hosomi, H. Yamagishi, T. Yamamoto, K. Bessho,
Y. Higo, K. Yamane, H. Yamada, M. Shoji, H.
Hachino, C. Fukumoto, H. Nagao, H. Kano, A novel
nonvolatile memory with spin torque transfer
magnetization switching spin-ram, Electron
Devices Meeting,2005. IEDM Technical Digest. IEEE
International, pp. 459-462.
CMOS sensing gt 0.2 V
S. Ikeda, J.Hayakawa, Y.M. Lee, F. Matsukura, Y.
Ohno, T. Hanyu and H. Ohno, Magnetic tunnel
junctions for spintronic memories and beyond,
IEEE Trans Elec. Dev. 54, 991 (2007).
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STT-RAM 2005
Sony
4 kb
M. Hosomi, H. Yamagishi, T. Yamamoto, K. Bessho,
Y. Higo, K. Yamane, H. Yamada, M. Shoji, H.
Hachino, C. Fukumoto, H. Nagao, H. Kano, A novel
nonvolatile memory with spin torque transfer
magnetization switching spin-ram, Electron
Devices Meeting,2005. IEDM Technical Digest. IEEE
International, pp. 459-462.
S. Ikeda, J.Hayakawa, Y.M. Lee, F. Matsukura, Y.
Ohno, T. Hanyu and H. Ohno, Magnetic tunnel
junctions for spintronic memories and beyond,
IEEE Trans Elec. Dev. 54, 991 (2007).
22
STT-RAM 2007
Grandis, Inc.
STT-RAM cell with integrated CMOS transistor. The
area of a single-level STT-RAM cell can be as
small as 6 F2.
Y. Huai, Z. Diao, Y.Ding, A. Panchula, S. Wang,
Z. Li, D. Apalkov, X. Luo, H. Nagai, A.
Driskill-Smith, and E. Chen, Spin Transfer
Torque RAM (STT-RAM) Technology, 2007 Inter.
Conf. Solid State Devices and Materials, Tsukuba,
2007, pp. 742-743.
S. Ikeda, J.Hayakawa, Y.M. Lee, F. Matsukura, Y.
Ohno, T. Hanyu and H. Ohno, Magnetic tunnel
junctions for spintronic memories and beyond,
IEEE Trans Elec. Dev. 54, 991 (2007).
Courtesy of Yiming Huai
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STT-RAM 2007
Hitachi
T. Kawahara, R. Takemura, K. Miura, J. Hayakawa,
S. Ikeda, Y.M. Lee, R. Sasaki, Y. Gotot, K. Ito,
T. Meguro, F. Matskura, H. Takahash, H. Matsuoka
and H. Ohno, 2 Mb SPRAM (Spin-Transfer Torque
RAM) with bit-by-bit bi-directional current write
and parallelizing-direction current read, IEEE J
Solid-State Circuits, 43, 109 (2008).
S. Ikeda, J.Hayakawa, Y.M. Lee, F. Matsukura, Y.
Ohno, T. Hanyu and H. Ohno, Magnetic tunnel
junctions for spintronic memories and beyond,
IEEE Trans Elec. Dev. 54, 991 (2007).
Courtesy of Hideo Ohno
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GMR and STT --- STT-RAM
T. Kawahara, R. Takemura, K. Miura, J. Hayakawa,
S. Ikeda, Y.M. Lee, R. Sasaki, Y. Gotot, K. Ito,
T. Meguro, F. Matskura, H. Takahash, H. Matsuoka
and H. Ohno, 2 Mb SPRAM (Spin-Transfer Torque
RAM) with bit-by-bit bi-directional current write
and parallelizing-direction current read, IEEE J
Solid-State Circuits, 43, 109 (2008).
25
STT-RAM Projections vs State-of-the-art
A.Driskill-Smith, Y. Huai, STT-RAM A New Spin
on Universal Memory, Future Fab, 23, 28
Hitachi, 2007
Yes
1.6 x 1.6 mm TMR 100 x 50 nm2 (60)
40 ns
100 ns
gt 109
40 pJ/100ns
None
1.8 V
T. Kawahara, R. Takemura, K. Miura, J. Hayakawa,
S. Ikeda, Y.M. Lee, R. Sasaki, Y. Gotot, K. Ito,
T. Meguro, F. Matskura, H. Takahash, H. Matsuoka
and H. Ohno, 2 Mb SPRAM (Spin-Transfer Torque
RAM) with bit-by-bit bi-directional current write
and parallelizing-direction current read, IEEE J
Solid-State Circuits, 43, 109 (2008).
26
STT-RAMProjections vs State-of-the-art
Nick Rizzo, Freescale
  Toggle MRAM (180 nm) Toggle MRAM (90 nm) DRAM (90 nm) SRAM (90 nm) FLASH (90 nm) FLASH (32 nm) ST MRAM (90 nm) ST MRAM (32 nm)
cell size (mm2) 1.25 0.25 0.05 1.3 0.06 0.01 0.06 0.01
Read time 35 ns 10 ns 10 ns 1.1 ns 10 - 50 ns 10 - 50 ns 10 ns 1 ns
Program time 5 ns 5 ns 10 ns 1.1 ns 0.1-100 ms 0.1-100 ms 10 ns 1 ns
Program energy/bit 150 pJ 120 pJ 5 pJ Needs refresh 5 pJ 30 120 nJ 10 nJ 0.4 pJ 0.04 pJ
Endurance gt 1015 gt 1015 gt 1015 gt 1015 gt 1015 read, gt 106 write gt 1015 read, gt 106 write gt 1015 gt1015
Non-volatility YES YES NO NO YES YES YES YES
Hitachi, 2007
1.6 x 1.6 mm TMR 100 x 50 nm2 (60)
40 ns
100 ns
40 pJ
gt 109
Yes
T. Kawahara, R. Takemura, K. Miura, J. Hayakawa,
S. Ikeda, Y.M. Lee, R. Sasaki, Y. Gotot, K. Ito,
T. Meguro, F. Matskura, H. Takahash, H. Matsuoka
and H. Ohno, 2 Mb SPRAM (Spin-Transfer Torque
RAM) with bit-by-bit bi-directional current write
and parallelizing-direction current read, IEEE J
Solid-State Circuits, 43, 109 (2008).
90nm, 32nm MRAM values are projected These
values are from the ITRS roadmap
27
Information Requested (2/2)
STT - RAM

• Current state-of-the-art using the provided
  metrics as a guide (Appendix 2 of request for
  white papers)
• CMOS integrated STT-RAM demonstrated. 2Mb
• Key scientific and technological issues remaining
  to accept the technology for manufacture.
• Lower critical currents and larger TMR ratio.
  Quality of the tunnel junction is critical.
• Technology roadmap outlining a 5-15 year develop
  path leading to manufacture in 5-10 years.
• Replace MRAM. Embedded memory in logic
  applications. Longer term universal memory.

28
Spin Transfer Torque Nano-oscillator
J. C. Slonczewski, Conductance and exchange
coupling of two ferromagnets separated by a
tunneling barrier, Phys. Rev. B, 39 6995 (1989).
Fixed
q
Free

• Spin transfer torque

29
Spin Transfer Torque Nano-oscillator
S. I. Kiselev, J. C. Sankey, I. N. Krivorotov, N.
C. Emley, R. J. Schoelkopf, R. A. Buhrman and D.
C. Ralph, Microwave oscillations of a nanomagnet
driven by a spin-polarized current, Nature,
425,380 (2003).
30 nmPt 2 nm Cu/ 3 nm Co/ 10 nm Cu/ 40 nmCo/ 80
nm Cu/
30
Spin Transfer Torque Nano-oscillator
S. I. Kiselev, J. C. Sankey, I. N. Krivorotov, N.
C. Emley, R. J. Schoelkopf, R. A. Buhrman and D.
C. Ralph, Microwave oscillations of a nanomagnet
driven by a spin-polarized current, Nature,
425,380 (2003).
30 nmPt 2 nm Cu/ 3 nm Co/ 10 nm Cu/ 40 nmCo/ 80
nm Cu/
Key element A skew magnetic field !
31
Spin Transfer Torque Nano-oscillator
30 nmPt 2 nm Cu/ 3 nm Co/ 10 nm Cu/ 40 nmCo/ 80
nm Cu/
0.2 nW estimated max.
32
Spin Transfer Torque Nano-oscillatorInjection
Locking
W. H. Rippard, M. R. Pufall, S. Kaka, T. J.
Silva, S. E. Russek, J. A. Katine, Injection
Locking and Phase Control of Spin Transfer
Nano-oscillators, Phys. Rev. Lett., 95, 067203
(2005).
1 nm Au 1 nm Cu/ 5 nm NiFe/ 4 nm Cu/ 20 nm
CoFe/ 50 nmCu/ 5 nm Ta/
30 pW
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Spin Transfer Torque Nano-oscillatorFrequency
Modulation
M. R. Pufall, W. H. Rippard, S. Kaka, T. J.
Silva, and S. E. Russek Frequency modulation of
spin-transfer oscillators Appl. Phys. Lett. 86,
082506 (2005).
250 pW
34
Spin Transfer Torque Nano-oscillatorPhase
Locking
S. Kaka, M.R. Pufall, W.H. Rippard, T.J. Silva,
S.E. Russek and J.A. Katine, Mutual
phase-locking of microwave spin torque
nano-oscillators Nature, 437, 389 (2005).
2 pW
35
Spin Transfer Torque Nano-oscillatorB0.0
T. Devoldera, A. Meftah, K. Ito, J. A. Katine, P.
Crozat and C. Chappert, Spin transfer
oscillators emitting microwave in zero applied
magnetic field, J. Appl. Phys. 101, 063916 2007.
lt 1.0 pW
Fixed layer
36
Spin Transfer Torque Nano-oscillatorPower
issues?
Some measures Cell phone 900 MHz, 1.8GHz,
500 mW Wireless access points 2.4 GHz, 5.0
GHz, 25 mW Automotive radar 24 GHz, 100 GHz
10 mW
State of the art STT nano-oscillators External
magnetic field, nW, efficiency 10-6
37
Spin Transfer Torque Nano-oscillator
30 nmPt 2 nm Cu/ 3 nm Co/ 10 nm Cu/ 40 nmCo/ 80
nm Cu/
MgO tunnel barrier
1 mW estimated
38
Spin Transfer Torque Nano-oscillatorPower
issues?
Some measures Cell phone 900 MHz, 1.8GHz,
500 mW Wireless access points 2.4 GHz, 5.0
GHz, 25 mW Automotive radar 24 GHz, 100 GHz
10 mW
State of the art STT nano-oscillators External
magnetic field, nW, efficiency 10-6
Projection MTJ based STT nano-oscillators mW,
efficiency 10-2 ? Power combining ? But
touch base with the Cornell, NIST, UVa
collaboration
39
Information Requested (2/2)
STT Nano-oscillators

• Current state-of-the-art using the provided
  metrics as a guide (Appendix 2 of request for
  white papers)
• Nano-oscillators at the nano-picowatt level with
  spin valve structures, in external magnetic
  fields. Existence proof of approach to external
  magnetic field free sustained oscillation.
  Phase locking, frequency modulation, injection
  locking demonstrated.
• Key scientific and technological issues remaining
  to accept the technology for manufacture.
• Increased power. Use of magnetic tunnel
  junctions. Power combining.
• Technology roadmap outlining a 5-15 year develop
  path leading to manufacture in 5-10 years.
• Needs to be guided by potential applications.

40
MRAM --- Spin Logic Device
Mark Rodwell, UC Santa Barbara
Eli Yablonovitch, UC Berkeley
transpinnor
I
source
Ikeda et. al., Japanese Journal of Applied
Physics, Vol. 44, No 48, pp. L1442-L1445
drain
41
Two views - Spin Logic
Output Power 1.610-8 W Total Power 2.510-8
W Efficiency65
Eli Yablonovitch
Mark Rodwell
Iinput
Iss
Ioutput
Inverter
Complementary Transpinnor logic

• Three state circuits
• memory and logic
• clocked logic
• 0 static dissipation

• Problems On/Off ratio is only about 51 Still
  takes too many ?Amps to switch

42
MRAM --- Spin Logic Device
Mark Rodwell, UC Santa Barbara
Eli Yablonovitch, UC Berkeley
transpinnor
I
source
Ikeda et. al., Japanese Journal of Applied
Physics, Vol. 44, No 48, pp. L1442-L1445
drain
43
GMR and STT --- Spin Logic Device?
Can we control GMR by Magnetostatically
coupling to a STT switch ??
Mark Rodwell, UC Santa Barbara
Eli Yablonovitch, UC Berkeley
transpinnor
I
source
drain
44
GMR and STT --- Spin Logic Device?
Can we control GMR by Magnetostatically
coupling to a STT switch ??
O. Ozatay,a_ N. C. Emley, P. M. Braganca, A. G.
F. Garcia, G. D. Fuchs, I. N. Krivorotov,R. A.
Buhrman, and D. C. Ralph, Spin transfer by
nonuniform current injection into a nanomagnet,
Appl. Phys. Lett., 88, 202502 (2006).
45
GMR and STT --- Spin Logic Device?
Input
Current driven Clocked logic Inherent memory,
ISS ? 0, no change in input of next stage
Output
ISS
ISS
M. Rodwell Inverter
Input
Output
46
GMR and STT --- Spin Logic Device?
M. Rodwell NAND Current controlled Clocked
logic 3-state, nonvolatile Cell 100F2 Energy
per bit 4 STT-RAM Switching speed
slower than STT-RAM
47
Information Requested (2/2)
GMR-STT Spin logic devices

• Current state-of-the-art using the provided
  metrics as a guide (Appendix 2 of request for
  white papers)
• Straw man concepts, synergistic with STT-RAM
  developments
• Key scientific and technological issues remaining
  to accept the technology for manufacture.
• Demonstration of magneto-static proximity
  coupling of GMR device and STT switch
• Technology roadmap outlining a 5-15 year develop
  path leading to manufacture in 5-10 years.
• Premature

48
Spin Torque Transfer Technology
A perspective STT-RAM will be developed for
memory embedded in logic
applications. STT Nano-oscillators development
needs to guided by
potential application. Research on
potential STT Logic will be
leveraged by developments in STT-RAM