T.Stobiecki Katedra Elektroniki AGH

1. Magnetic Tunnel Junction (MTJ)or Tunnel Magnetoresistance (TMR)orJunction Magneto- Resistance (JMR) T.Stobiecki Katedra Elektroniki AGH 11 wykład 13.12.2004

11. Material Polarizations Ni 33 % Co 42 % Fe 45 % Ni80 Fe20 48 % Co84 Fe16 55 % CoFeB 60% Spin Polarization, Density of States Density of states3d Spin Polarization Normal metal (Cu) Ferromagnetic metal (Fe)

13. eV FM I (PI) FM II (PII) Barrier Tunneling inFM/I/FM junction

18. FM FM FM I I I FM FM FM AF I B FM Type of MTJs Spin valve junction (SV- MTJ) Standard junction Double barrier junction

19. Application-Oriented Properties of S-V MTJ SV-MTJ • 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 • Tunnel Magnetoresistance -TMR • Resistance area product -RxA Magnetic Electric • Interlayer coupling field HS • Exchange bias field HEXB • Coercive field pinned HCP • and free HCF layer • Switching field HSF

20. Interlayer coupling HS Exchange coupling HEXB FM I (Free) I FM II(Pinned) AF B Magnetic and ElectricParameters HCF HS HEXB HCP HSF HSF switching fields

21. SENSORS M-RAM SV-MTJ SPIN-LOGIC READ HEADS Applications of SV-MTJ

22. Critical switching fields Hx ,Hy (S-W) asteroid 1 Hy/H(0) 0 -1 1 -1 0 SV-MTJ Based MRAM 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 Motorola: S.Tehrani et al. PROCEEDINGS OF THE IEEE, VOL. 91, NO. 5, MAY 2003

23. 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 3.3V 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

24. SV-MTJ Based Spin Logic Gates VOUT= IS(RMTJ3 + RMTJ3 – RMTJ1 – RMTJ2) 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 Siemens & Univ. Bielefeld: R. Richter et al. J. Magn.Magn. Mat. 240 (2002) 127–129

25. 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

26. 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

27. 0 10 30 60 100 Au 25 nm Ta 3 nm Cu 30 nm Ta 5 nm Ta 5 nm NiFe 3 nm 10 mm Al2O3 1.4nm 3 6 10 30 50 NiFe x nm CoFe t nm MnIr 12 nm CoFe 2.5 nm Cu 25 nm Substrate Si (100) Al2O3 1.4 nm CoFe 2.5 nm MnIr 10 nm Cu 5 nm NiFe 2 nm Ta 5 nm Cu 10 nm Ta 5 nm SiO2 Substrate Si (100) Experiments on SV -MTJs A MTJs B MTJs Junction Junctions size (180180) m2 Junction A structure prof. G. Reiss laboratory University Bielefeld B structure prof. T. Takahasi laboratory, Tohoku University

28. Effect of Annealing on TMR H=80 kA/m 10 mm annealing 1 hour in vacuum 10-6 hPa As deposited Annealed

29. Interlayer and Exchange Coupling Fields Interlayer coupling fields Exchange coupling fields A MTJs B MTJs

30. Interlayer and Exchange Coupling Fields

31. Temperature Dependence of TMR P. Wiśniowski, M.Rams,... Temperature dependence of tunnel magnetoresistance of IrMn based MTJ, phys. stat. sol (2004)

32. Total Conductance Varies slightly with T Varieswith T as magnetization does Bloch law Dominant Negligible

33. P AP 100 nm Polarization, Bloch Law 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)

34. Spin Independent Conductance Hopping conductance, high level of defects Hopping conductance, low level of defects

35. 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 Clean room Multi (10) Target Module Oxidation / Pre-clean Module Transport Module

37. Metal depo. LL１: wafer-in Plasma Oxidation LL２: Bridge Reactive sputter : surface smooth Sputtering System

39. Measurements MOKE R-VSM

40. MOKE with Orthogonal Coils