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Properties and Fabricating Technique of Tunneling Magnetoresistance Reporter : Kuo-Ming Wu Day : 2006/04/08
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Outline Development of Spintronics Tunneling Magnetoresistance Spin Torque Transfer Conclusion
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Development of Spintronics Spin electronic : Spintronics The spin induced ferromagnetic phenomena has a large application valuation, and hence builds on the Spintronics that the device working principle depends on the electron spin direction.
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Development of Spintronics The lower density of state of the spin-up than that of spin-down one at Fermi-level energy. The majority and minority spin electrons play important roles of the magneto-electric behaviors, such as magnetoresistance(MR).
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Development of Spintronics The MR ratio is the variation of the sample resistance under different magnetic field.
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Development of Spintronics TypeOrderFieldTemperature OMR10 -2 %1 TRT AMR2 %10 OeRT GMR5 %10 OeRT CMR10 6 %5 T100 K TMR10 2 %10 0~1 OeRT
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Tunneling Magnetoresistance The energy band structure the 3d ferromagnetic materials near the Fermi level, such as Fe, Co, Ni EFEF MajorityMinority n ↑ (E F )n ↓ (E F )
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Tunneling Magnetoresistance ↑↑ Parallel-state
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Tunneling Magnetoresistance ↑↓ AntiParallel-state
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Tunneling Magnetoresistance M. Julliere Phys. Lett. A 54 225 (1975)
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Tunneling Magnetoresistance J. G. Simmons, J. Appl. Phys. 34,2581(1963)
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Tunneling Magnetoresistance → → ← ← → ← ← → → → ← ← → ← ← → Ta 20/CoFe 25/AlOx 1.2/NiFe 30/Ta 40
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Tunneling Magnetoresistance Ta 20/CoFe 25/AlOx 1.2 or 1.5/NiFe 30/Ta 40 AlOx thicknessBarrier WidthBarrier HeightInaccuracy 1.2 nm1.126 nm2.793 eV0.255 % 1.5 nm1.482 nm1.839 eV0.290 %
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Tunneling Magnetoresistance Ta 20/MnIr 12/CoFe 3/AlOx 1.2/CoFe 3 /NiFe 45/Ta 20 → → ← ← → ← ← → ← ← → ← ← → → →
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Spin Torque Transfer Jc:5x10 6 A/cm 2 → ←
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Spin Torque Transfer In 1996, Slonczewski and Berger predicted that the magnetization of a magnetic layer can be reversed by injection of a spin polarized current and spin transfer to the layer. Magnetization reversal without application of an external magnetic field would be of considerable interest to switch magnetic microdevices.
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Spin Torque Transfer Slonczewski brought out that polarized spin current contribute torque is equal to: Where γis the gyromagnetic ratio H eff is effect magnetic field c is the direction of symmetry axis of anisotropy αis the damping coefficient
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Spin Torque Transfer Write to parallel
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Spin Torque Transfer Write to antiparallel
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Spin Torque Transfer SiO 2 /Ta 20nm/PtMn 15nm/CoFeB 3nm/Ru 0.8nm/ CoFeB 3nm / AlOx 0.7 before oxide/CoFeB 2nm/Ta 40 nm → ←
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Spin Torque Transfer Beam holder 45° etching holder Beam 75° etching holder Beam 0° etching Redeposition
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Spin Torque Transfer
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Wafer Coil Source Chamber Process Chamber ICP Power (13.56 MHz) Bias Power (13.56 MHz) Coller Inductively Coupled Plasma Reactive Ion Etching
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Spin Torque Transfer
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500 x 250 nm130 x 130 nm
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Spin Torque Transfer
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Conclusion Spin torque transfer effect is more competent than field induced switching for TMR or GMR nano-devices. ICP-RIE etching procures higher taper angle and less damage than Ion Beam Etching for TMR fabrication process.
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Thank You For Your Attention
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