Physical Mechanisms Affecting Performance of Perpendicular STT MRAM Cells

Spin transfer torque magnetoresistive random access memory (STT MRAM) is an alternative to SRAM [1] and Flash [2] , [3] in various embedded applications, as it can provide non-volatility concurrently with low power, high speed operation, and high endurance. In order to become a viable option for replacing DRAM as a stand-alone memory at relevant areal densities, further optimization of MRAM performance is needed, as continued technology scaling and advanced computing systems impose challenging specifications on MRAM in terms of its retention (thermal stability), read-out latencies, and write margins [4] . This talk will present our recent experimental, theoretical, and modeling results on understanding physical mechanisms that affect performance of perpendicular STT-MRAM cells under electrical, magnetic and thermal excitations. In particular, we will report experimental and modeling results that extend of our recent work on electrical self-heating in STT-MRAM [5] to smaller device size, describe our work on optimization of FL materials for improving STT efficiency and thermal stability [6] , present analytical model for calculating energy barrier for domain-wall-mediated magnetization reversal of the perpendicular FL [7] , and show our experimental results which suggest that, contrary to common understanding, fitting the magnetic-field switching probabilities P(H) to a macrospin-reversal model provides approximately correct values of perpendicular magnetic anisotropy field H k on device level.