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A Review of MTJ Compact Models

Literature Review. A Review of MTJ Compact Models. Richard Dorrance Advisor: Prof. Dejan Marković April 15, 2011. STT-MRAM and How it Works. STT = Spin-Torque-Transfer Use current to flip free layer between two resistive states. Compact Model Requirments. Bias Voltage. Temperature.

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A Review of MTJ Compact Models

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  1. Literature Review A Review ofMTJ Compact Models Richard DorranceAdvisor: Prof. Dejan Marković April 15, 2011

  2. STT-MRAM and How it Works • STT = Spin-Torque-Transfer • Use current to flip free layerbetween two resistive states

  3. Compact Model Requirments Bias Voltage Temperature Regions of Operation Probabilistic Switching

  4. [1] J. D. Harms, et al. (U. Minnesota) • Switching time vs. current fitting. • User defined delay for switching. • SPICE.

  5. [2] A. Nigam, et al. (UVA & Grandis) • Calculate the total transmission probability and density of available states (implemented in SPICE). • Accuracy: ±10% RP, RAP, TMR • Physics based… I think… Measured Model

  6. [3] L.-B. Faber, et al. (U. Paris XI) • Model switching probabilities across several parameters. • Switching based on user defined threshold and delay. • Inaccurate below 10ns pulse widths. Switching Probabilities Spectre Model

  7. [4] A. Raychowdhury, (Intel) • Uses a linearized LLGE, modified/fitted for thermally activated switching. Crude bias voltage approximation. • Semi- physics, semi-empirical.

  8. [5] D. Datta, et al. (Purdue & UCB) • Uses a Non-Equilibrium Green’s Function (NEGF) based quantum transport model. (Physics Based) Voltage Bias Out of Plain Fields

  9. [6] M. Madec, et al. (ULP) • Traditional LLGE model for precessional switching. • Modified Jullière conductance model to include bias voltage dependencies. • Thermally activated switching not considered. • VHDL-AMS implementation.

  10. Limitations of Current Models • Few model bias voltage dependencies. • No published model incorporates temperature effects. • Empirical models cannot predict behavior. • Most physics models are too cumbersome for compact modeling. • Most models are ill-suited for incorporating statistical variation.

  11. References • J. D. Harms, et al., “SPICE Macromodel of Spin-Torque-Transfer-Operated Magnetic Tunnel Junctions,” IEEE Transactions on Electron Devices, vol. 57, no. 6, pp. 1425-1430, June 2010. • A. Nigam, et al., “Self Consistent Parameterized Physical MTJ Compact Model for STT-RAM,” CAS 2010, vol. 2, pp. 423-426, Oct. 2010. • L.-B. Faber, et al., “Dynamic Compact Model of Spin-Transfer Torque Based Magnetic Tunnel Junction (MTJ),” DTIS '09, pp. 130-135, April 2009. • A. Raychowdhury, “Model Study of 1T-1STT MTJ” MWSCAS 2010, pp. 5-8, Aug. 2010. • D. Datta, et al., “Quantitative Model for TMR and Spin-Transfer Torque in MTJ Devices,” IEDM 2010, pp. 22.8.1-22.8.4, Dec. 2010. • M. Madec, et al., “Compact Modeling of Magnetic Tunnel Junction,” NEWCAS-TAISA 2008,pp.229-232, June 2008.

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