ITRS Emerging Technology Review, 12 July 2008 Contact: SJ Allen, allen@iqcd.ucsb.edu 1 Spin Torque...

transcript

ITRS Emerging Technology Review, 12 July 2008 Contact: SJ Allen, allen@iqcd.ucsb.edu1

Spin Torque Transfer Technology

S. James AllenUC Santa Barbara

• Science

• TechnologySpin Torque Transfer – RAM, STT-RAM

Spin Torque Transfer Nano-oscillators Spin logic devices

Mark Rodwell UC Santa BarbaraBob Buhrman CornellStu Wolf U. VirginiaH. Ohno Tohoku UniversityNick Rizzo Free ScaleYiming Huai GrandisBill Rippard NISTSteve Russek NISTEli Yablonovitch UC BerkeleyAjey Jacob Intel

With input from

• Science

From R. A. Buhrman, “Spin Torque Effects in Magnetic Nanostructures”, Spintech IV, 2007

Spin Torque Transfer: Science

• Heisenberg exchange

• Giant magneto resistance

• Spin transfer torque

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 FerromagnetNo

Ef , 1-band

Anti-ferromagnetic Anti-ferromagnetic

Ferromagnetic

Ferromagnet Ferromagnet

Ef , 1-band

1 cos/

(1 )I V G G

( (0)) 2

0 (1 )

P = 1, ideal, perfect spin valve

H. Ohno, “Spintronics” Seminar, UCSB May, 2008

( (0)) 2

Fixed SyF

FreeM. 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.

Effective field

Damping

o AHdm

Slonczewski torque

Effect

Effective field

Damping

ive magnetic field/

J em m

Slonczewski torque

Effecti

Effective field

Damping

ve magnetic fie d/

J em m

• Precession• Switching• Damping

• Science

From R. A. Buhrman, “Spin Torque Effects in Magnetic Nanostructures”, Spintech IV, 2007

GMR and STT --- STT-RAM

Slonczewski torque

Effecti

Effective field

Damping

ve magnetic fie d/

J em m

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 A

Conventional MRAM (toggle) and Spin Torque MRAM

H field produces torque to reverse free layer. Spin polarized current 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 m x 0.12 m bit.•Isw reduces as bit scales smaller.

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.

Fixed SyF

STT-RAM 2005

CMOS driver 100 100 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).

STT-RAM 2005

CMOS sensing > 0.2 V

Read ~ 0.2 V < write!

STT-RAM 2005

STT-RAM 2007

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.

STT-RAM cell with integrated CMOS transistor. The area of a single-level STT-RAM cell can be as small as 6 F2.

Grandis, Inc.

Courtesy of Yiming Huai

115 x 180 nm2

STT-RAM 2007

Hitachi

Courtesy of Hideo Ohno

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

1.6 x 1.6 m TMR 100 x 50 nm2 (60)

100 ns

40 pJ/100ns

STT-RAMProjections vs State-of-the-art

Hitachi, 2007

1.6 x 1.6 m TMR 100 x 50 nm2 (60)

100 ns

Toggle

MRAM (180 nm)

ToggleMRAM (90 nm)*

DRAM(90 nm)+

SRAM(90 nm)+

FLASH(90 nm)+

FLASH(32 nm)+

ST MRAM

(90 nm)*

STMRAM

(32 nm)*

cell size (m2)

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 pJ5 pJ

Needs refresh

5 pJ30 – 120

nJ10 nJ 0.4 pJ 0.04 pJ

Endurance > 1015 > 1015 > 1015 > 1015

> 1015 read,

> 106 write

> 1015 read,

> 106 write> 1015 >1015

Non-volatility

YES YES NO NO YES YES YES YES

* 90nm, 32nm MRAM values are projected+ These values are from the ITRS roadmap

Nick Rizzo, Freescale

Information Requested (2/2)

• 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.

STT - RAM

Spin Transfer Torque Nano-oscillator

Slonczewski torque

Effecti

Effective field

Damping

ve magnetic fie d/

J em m

30 nmPt2 nm Cu/3 nm Co/10 nm Cu/40 nmCo/80 nm Cu/

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).“

~ 0.1 nW measured

130 x 70 nm2

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).“

~ 0.1 nW measured

130 x 70 nm2

Key element: A skew magnetic field !

1 1 50 1

2 2 50 50DCP I RR

~ 0.1 nW measured

~ 0.2 nW estimated max.

610 Efficiency

130 x 70 nm2

Cu junction

Spin Transfer Torque Nano-oscillator:

Injection Locking

1 nm Au1 nm Cu/5 nm NiFe/4 nm Cu/20 nm CoFe/50 nmCu/5 nm Ta/

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).

50 x 50 nm2

0.56 Tesla

~ 30 pW

Frequency ModulationM. 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

Phase LockingS. 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

B=0.0T. 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.

Effective field, shape, material

/Slonczewski torqu

/Effective magnetic fiel

dtJ e P

m p mt M

J e Pm

Fixed layer

< 1.0 pW

Power issues?

Some measures:Cell phone – 900 MHz, 1.8GHz, ~ 500 mWWireless access points – 2.4 GHz, 5.0 GHz, ~ 25 mWAutomotive radar 24 GHz, 100 GHz ~ 10 mW

State of the art STT nano-oscillatorsExternal magnetic field, ~ nW, efficiency 10-6

1 1 50 1

2 2 50 50DCP I RR

Cu junction

MgO tunnel barrier

~ 1 W estimated 210Efficiency

Power issues?

Some measures:Cell phone – 900 MHz, 1.8GHz, ~ 500 mWWireless access points – 2.4 GHz, 5.0 GHz, ~ 25 mWAutomotive radar 24 GHz, 100 GHz ~ 10 mW

State of the art STT nano-oscillatorsExternal magnetic field, ~ nW, efficiency ~ 10-6

ProjectionMTJ based STT nano-oscillators ~ W, efficiency ~ 10-2 ?Power combining ?

But touch base with the Cornell, NIST, UVa collaboration

• 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.

STT Nano-oscillators

“MRAM” --- Spin Logic Device

Mark Rodwell, UC Santa BarbaraHigh

Eli Yablonovitch, UC Berkeley

source

“transpinnor”Si (001) Substrate

Ta 5nm

Ru 50nm

Ta 5nm

NiFe 5nm

Antiferromagnetic MnIr 8nm

CoFe 2nm

Ru 0.8nm

Ferromagnetic CoFeB 3nm

MgO 1.5nm Tunnel Barrier

Ta 5nm

Ru 15nm

Isignal

Magnetization

Source

InsulatorCurrent Gate

BField

Device Area 1?m2

Ikeda et. al., Japanese Journal of Applied Physics, Vol. 44, No 48, pp. L1442-L1445

• Current controlled• Non-volatile• “Leaky” switch, ~ 6

Two views - Spin Logic

5μA output5μA input

500Ωor

2.275kΩ

2.275kΩor

+V +3mV

-V -3mV

Output Power = 1.6*10-8 WTotal Power = 2.5*10-8 W

Efficiency=65%

•Problems: On/Off ratio is only about 5:1 Still takes too many Amps to switch

Eli Yablonovitch

Complementary Transpinnor logic

output

Mark Rodwell

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

Inverter

Iinput

Ioutput

Iinput

Ioutput

“MRAM” --- Spin Logic Device

source

“transpinnor”Si (001) Substrate

Ta 5nm

Ru 50nm

Ta 5nm

NiFe 5nm

Antiferromagnetic MnIr 8nm

CoFe 2nm

Ru 0.8nm

MgO 1.5nm Tunnel Barrier

Ta 5nm

Ru 15nm

Isignal

Magnetization

Source

InsulatorCurrent Gate

BField

Device Area 1?m2

Ikeda et. al., Japanese Journal of Applied Physics, Vol. 44, No 48, pp. L1442-L1445

• Current controlled• Non-volatile• “Leaky” switch, ~ 6

GMR and STT --- Spin Logic Device?

source

“transpinnor”Fixed

Contact

Contact Contact

Contact

STT – “switch control”GMR – “switch”

Magnetostatically coupled free layers

Can we control GMR by Magnetostatically coupling to a STT switch ??

Contact

Contact Contact

Contact

STT – “switch control”GMR – “switch”

Magnetostatically coupled free layers

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).

Output

Current drivenClocked logicInherent memory, ISS → 0, no change in input of next stage

output

M. Rodwell Inverter

B Input

O utput

A Input

B Input

O utput

A Input

M. Rodwell NAND

Current controlledClocked logic3-state, nonvolatile

Cell 100F2

Energy per bit ~ 4* STT-RAMSwitching speed slower than STT-RAM

• 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

GMR-STT Spin logic devices

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

ITRS Emerging Technology Review, 12 July 2008 Contact: SJ Allen, allen@iqcd.ucsb.edu 1 Spin Torque...

Documents