Modeling of Single-Digit Nanometer Perpendicular Shape Anisotropy Magnetic Tunnel Junction Driven by Spin-Transfer-Torque

Spin Transfer Torque Magnetic Random-Access Memory (STT-MRAM) has become one of the leading candidates for next generation memory applications. One of the key challenges is the simultaneous achievement of low switching current, high thermal stability and large TMR. Low switching current can be achieved by the shrinkage of the device size. However, the thermal stability of the perpendicular magnetic tunnel junction (P-MTJ) is severely damaged with the reduced size. The concept of Perpendicular Shape Anisotropy (PSA) MTJ is proposed recently, in which thicker free layer is adopted to keep the required thermal stability in single-digit nanometers. In this way, relative high thermal stability can be achieved even the size down to sub-tO-nm. The device shows possible application in the nanometer scale and is compatible with the developed CMOS technology nodes. The SPICE model of the PSA-MTJ device is highly required since its operation principle is different from the incumbent STT -MT J device. In this paper, a dynamic model of the PSA-MTJ is developed, including its micromagnetic simulation using LLG equation. In the developed model, the stochastic term is included to denote the effects in nanometer scale. In this way, the accuracy is improved. By analyzing the instantaneous magnetization vector, the switching time is extracted. The impacts of the write voltage scaling on the switching time, the energy consumption and the write failure rate of PSA-MTJ are studied. Based on the model, both the static and dynamic behaviors can be simulated. The scale effect of the PMA device is also studied based on the developed model. Finally, hybrid MTJ/CMOS simulation is performed to validate the developed model for circuit designs and simulations in the single-digit nanometer scale.