Physics-Based SPICE-Compatible Compact Model for Simulating Hybrid MTJ/CMOS Circuits

Abstract

A simulation framework that can comprehend the impact of material changes from the device level to the system level design can be of great value, especially to evaluate the impact of emerging devices on various applications. To that effect, we developed a SPICE-based hybrid magnetic tunnel junction (MTJ)/CMOS simulator, which can be used to explore new opportunities in large scale system design. In the proposed simulation framework, MTJ modeling is based on Landau-Lifshitz-Gilbert (LLG) equation incorporating both spin-torque and external magnetic field(s). LLG, along with heat diffusion equation, thermal variations, and electron transport, is implemented using SPICE-in-built voltage-dependent current sources and capacitors. The proposed simulation framework is flexible because the physical device parameters such as MgO thickness, ferromagnet material anisotropy (Ku), and device dimensions are user-defined parameters. Furthermore, we benchmarked this model with experiments in terms of switching current density (JC), switching time (TSWITCH), and tunneling magnetoresistance. Finally, we used the simulation framework to study different MTJ structures, such as in-plane magnet anisotropy and perpendicular magnet anisotropy, the impact of parametric process variations and temperature on the yield of spin transfer torque magnetoresistive random access memories, magnetic flip-flops, and spin-torque oscillators.