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

3. 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, (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, (1989).
Non-magnetic
Ferromagnet
Ef , 1-band
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, (1989).
Ferromagnet
Ef , 1-band
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, (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
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
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, (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, (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, (1989).
Precession
Switching
Damping
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 Spin transfer torque Precession Switching
J. C. Slonczewski, “Conductance and exchange coupling of two ferromagnets separated by a tunneling barrier”, Phys. Rev. B, (1989).
Precession
Switching
Damping
Fixed q
Free
Spin transfer torque

16. GMR and STT --- STT-RAM ~ 200 mA
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 < 1 mA/bit for 0.06 mm x 0.12 mm bit.
Isw reduces as bit scales smaller.

18. STT-RAM
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

19. STT-RAM 2005 CMOS driver 100 mA/100 nm
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
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).

20. STT-RAM 2005 Read ~ 0.2 V < write! CMOS sensing > 0.2 V
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
CMOS sensing > 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).

21. STT-RAM
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
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. 115 x 180 nm2 Courtesy of Yiming Huai
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
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

23. STT-RAM 2007 Hitachi Courtesy of Hideo Ohno
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

24. 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
> 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-RAM Projections vs State-of-the-art
Nick Rizzo, Freescale
Toggle
MRAM
(180 nm)
(90 nm)*
DRAM
(90 nm)+
SRAM
FLASH
(32 nm)+
ST MRAM ST
(32 nm)*
cell size (mm2)
1.25
0.25
0.05
1.3
0.06
0.01
Read time
35 ns
10 ns
1.1 ns ns
1 ns
Program time
5 ns ms
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
> 1015
> 1015 read,
> 106 write
>1015
Non-volatility
YES NO
Hitachi, 2007
1.6 x 1.6 mm TMR 100 x 50 nm2 (60)
40 ns
100 ns
40 pJ
> 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, (1989).
Precession
Switching
Damping
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/
~ 0.1 nW measured H
130 x 70 nm2

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/
~ 0.1 nW measured H
130 x 70 nm2
Key element: A skew magnetic field !

31. Spin Transfer Torque Nano-oscillator
~ 0.1 nW measured
30 nmPt
2 nm Cu/
3 nm Co/
10 nm Cu/
40 nmCo/
80 nm Cu/ H
130 x 70 nm2
~ 0.2 nW estimated max.

32. Spin Transfer Torque Nano-oscillator: Injection 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, (2005).
1 nm Au
1 nm Cu/
5 nm NiFe/
4 nm Cu/
20 nm CoFe/
50 nmCu/
5 nm Ta/
50 x 50 nm2
0.56 Tesla
~ 30 pW

33. Spin Transfer Torque Nano-oscillator: Frequency 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, (2005).
~ 250 pW

34. Spin Transfer Torque Nano-oscillator: Phase 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-oscillator: B=0.0
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,
< 1.0 pW
Fixed layer
Free

36. Spin Transfer Torque Nano-oscillator: Power 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-oscillator: Power 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
Current controlled
Non-volatile
“Leaky” switch,
Mark Rodwell, UC Santa Barbara
Eli Yablonovitch, UC Berkeley I
“transpinnor”
source
Ikeda et. al., Japanese Journal of Applied Physics, Vol. 44, No 48, pp. L1442-L1445
drain

41. Two views - Spin Logic Eli Yablonovitch Mark Rodwell
Output Power = 1.6*10-8 W
Total Power = 2.5*10-8 W
Efficiency=65%
Eli Yablonovitch
5μA output
5μA input
500Ω or
2.275kΩ +V
+3mV -V
-3mV
Mark Rodwell
Iss
Iinput
Iinput
Iss
Ioutput
Ioutput
Inverter
Complementary
Transpinnor logic
Three state circuits
memory and logic
clocked logic
“0” static dissipation
Problems: On/Off ratio is only about 5:1 Still takes too many Amps to switch

42. “MRAM” --- Spin Logic Device
Current controlled
Non-volatile
“Leaky” switch,
Mark Rodwell, UC Santa Barbara
Eli Yablonovitch, UC Berkeley I
“transpinnor”
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 I
“transpinnor”
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, (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