Modeling and Optimization of Two-Terminal Spin-Orbit-Torque MRAM

TL;DR

This paper models and benchmarks 2T-SOT-MRAM, showing that emerging out-of-plane SOT materials significantly reduce write energy, especially at smaller device scales, and proposes a novel device design for improved efficiency.

Contribution

It introduces a physical model and benchmarking results for 2T-SOT-MRAM, highlighting the potential of out-of-plane SOT materials and a new device structure for energy-efficient memory.

Findings

Out-of-plane SOT materials can greatly reduce write energy.

Scaling down device size enhances energy efficiency.

Proposed device design increases spin current and efficiency.

Abstract

This paper presents physical modeling and benchmarking for two-terminal spin-orbit torque magnetic random-access memory (2T-SOT-MRAM). The results indicate that the common SOT materials that provide only in-plane torque can provide little to no improvement over spin-transfer-torque (STT) MRAM in terms of write energy. However, emerging SOT materials that provide out-of-plane torques with efficiencies as small as 0.1 can result in significant improvements in the write energy for such 2-terminal devices, especially when the magnet lateral dimensions are scaled down to 30 or 20 nm. Additionally, a novel 2T-SOT MRAM device is proposed that can increase the path electrons pass through the SOT layer; hence, increasing the generated spin current and the energy efficiency of the device. Our benchmarking results indicate that an out-of-plane SOT efficiency of 0.051 for 20nm wide devices can result in write energies approaching SRAM at the 7nm technology node.