A portable dynamics switching model for perpendicular magnetic tunnel junctions considering both thermal and process variations

Abstract

Spin-transfer torque magnetic random access memory (STT-MRAM) has become a promising candidate for future nonvolatile and universal memory because it features non-volatility, fast access time, almost unlimited programming endurance and zero standby power [1-2]. The magnetic tunneling junction (MTJ) is the fundamental building element of STT-MRAM. An MTJ consists of two ferromagnetic layers (a free layer, FL and a reference layer, RL) separated by a thin tunneling dielectric film. The magnetization of the FL can be set as parallel or anti-parallel with the RL by a spin polarized current, which leads to low or high resistance state of the MTJ. The applications of STT-MRAM have been successfully demonstrated [3-4]. However, like all the other nanotechnologies, STT-MRAM suffers from process variations and environment fluctuations, such as thermal fluctuations, which significantly affect the performance and stability of MTJ devices. Several studies have been performed to address the impact of the process variations on the reliability of STT-MRAM and the thermal fluctuation effects on the magnetization switching [5-6]. These works either need costly Monte-Carlo simulations with complex macro-magnetic and SPICE models or do not integrate both effects of the thermal fluctuation and process variations. Wang et al [7] developed a compact MTJ switching model for MTJs derived from the macro-magnetic modeling to simulate the statistical electrical and magnetic properties of MTJ due to both thermal fluctuation and process variations; however it is restricted for in-plane MTJs.