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

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

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

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

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 Ferromagnet Ef , 1-band Ferromagnet Heisenberg exchange Giant magneto resistance Spin transfer torque

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). Ferromagnet Ef , 1-band Ferromagnet Ferromagnetic Ferromagnetic Anti-ferromagnetic Anti-ferromagnetic Heisenberg exchange

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

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

H. Ohno, “Spintronics” Seminar, UCSB May, 2008 ideal, perfect spin valve

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

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

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

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). Precession Switching Damping Fixed q Free Spin transfer torque

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

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, 39 6995 (1989). Precession Switching Damping Fixed q Free Spin transfer torque

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

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.

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.

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. 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).

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. 459-462. 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).

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).

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. 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

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

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).

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).

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 10 - 50 ns 1 ns Program time 5 ns 0.1-100 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

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.

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). Precession Switching Damping Fixed q Free Spin transfer torque

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

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 !

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.

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, 067203 (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

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, 082506 (2005). ~ 250 pW

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

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, 063916 2007. < 1.0 pW Fixed layer Free

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

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

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

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.

“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

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

“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

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

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).

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

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

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

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