1. Properties and Fabricating Technique of Tunneling Magnetoresistance Reporter : Kuo-Ming Wu Day ： 2006/04/08

2. Outline Development of Spintronics Tunneling Magnetoresistance Spin Torque Transfer Conclusion

3. 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.

4. 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).

5. Development of Spintronics The MR ratio is the variation of the sample resistance under different magnetic field.

6. 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

7. 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 )

8. Tunneling Magnetoresistance ↑↑ Parallel-state

9. Tunneling Magnetoresistance ↑↓ AntiParallel-state

10. Tunneling Magnetoresistance M. Julliere Phys. Lett. A 54 225 (1975)

11. Tunneling Magnetoresistance J. G. Simmons, J. Appl. Phys. 34,2581(1963)

12. Tunneling Magnetoresistance → → ← ← → ← ← → → → ← ← → ← ← → Ta 20/CoFe 25/AlOx 1.2/NiFe 30/Ta 40

13. 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 %

14. Tunneling Magnetoresistance Ta 20/MnIr 12/CoFe 3/AlOx 1.2/CoFe 3 /NiFe 45/Ta 20 → → ← ← → ← ← → ← ← → ← ← → → →

15. Spin Torque Transfer Jc:5x10 6 A/cm 2 → ←

16. 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.

17. 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

18. Spin Torque Transfer Write to parallel

19. Spin Torque Transfer Write to antiparallel

20. 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 → ←

21. Spin Torque Transfer Beam holder 45° etching holder Beam 75° etching holder Beam 0° etching Redeposition

22. Spin Torque Transfer

24. Wafer Coil Source Chamber Process Chamber ICP Power (13.56 MHz) Bias Power (13.56 MHz) Coller Inductively Coupled Plasma Reactive Ion Etching

25. Spin Torque Transfer

26. 500 x 250 nm130 x 130 nm

27. Spin Torque Transfer

29. 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.

30. Thank You For Your Attention