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MRAM initiative

MRAM initiative. Bob White, Department of ECE Jimmy Zhu, Department of ECE Jim Hoburg, Department of ECE Katayun Barmak, Department of MSE Chando Park, CIT Xiaochun Zhu, Department of ECE. Program Objective. To understand the scalability of MRAM technology

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MRAM initiative

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  1. MRAM initiative • Bob White, Department of ECE • Jimmy Zhu, Department of ECE • Jim Hoburg, Department of ECE • Katayun Barmak, Department of MSE • Chando Park, CIT • Xiaochun Zhu, Department of ECE

  2. Program Objective • To understand the scalability of MRAM technology • To develop innovative architectures that enable scaling

  3. Scaling Reduce metal pitch Write Current? Thermal Stability?

  4. Overview of initiative Micromagnetic Modeling Memory element shape Finite Element Modeling Cell design Shielded conductors Test Structure High △/  Fe3O4 ? Fabrication Thermal assist

  5. Examples of simulated domain configurations for different shape elements: NiFe: D=1mm Fe (100) Co: D=1mm NiFe: 1mm Switching of various shaped elements: 0.1mm 0.2mm Memory element shape

  6. Very low switching current, low operating power. • Robust magnetic switching. • 4 F2 memory element size. read line Write line • Good thermal stability. Down-size scaling “0” state “1” state Cell design

  7. Fe3O4 2,400 % TMR CoFe 41 % TMR High △/  Tunneling Magnetoresistance Ratio vs. Polarization

  8. 8Å I 10Å half-select elements NiFeCo(15Å) Thermally Activated Switching Probability

  9. Exchange field at room temperature Writing Exchange Field Temperature ( oC) Thermal assist

  10. Shielded conductors • Micromagnetic : Jimmy Zhu • Macromagnetic : Jim Hoburg

  11. Macromagnetic (finite element) modeling of shielded conductors

  12. Redirection of flux with shielded conductor

  13. Components of flux density in memory cell: shielded conductor

  14. Operating points on B-H characteristic:linear portion of nonlinear simulation

  15. Components of flux density in memory cell: unshielded conductor

  16. Extended shield

  17. Partially extended shield

  18. Thick horizontal leg

  19. Thin vertical legs

  20. Eddy current solution (f = 125 MHz) phase 0: phase 90:

  21. Magnetic 150nm 50nm 100nm 100nm 200nm y Parameters: Ms = 800 emu/cc, A= 1.0x10-6 erg/cm x Mesh size: 5nm z Dynamics: Micromagnetic modeling of shielded conductors

  22. Comparison of macromagnetic and micromagnetic results: horizontal field in memory cell

  23. Comparison of macromagnetic and micromagnetic results: vertical field in memory cell

  24. Conclusions(regarding shielded conductors) • Factor of 2 increase in field in cell (or factor of 2 decrease in current) • Field in cell can be made more uniform through shield design • Eddy currents not significant • Macromodeling and micromodeling yield same results

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