High-Density, Low-Power Voltage-Control Spin Orbit Torque Memory with Synchronous Two-Step Write and Symmetric Read Techniques

Abstract

Voltage-control spin orbit torque (VC-SOT) magnetic tunnel junction (MTJ) has the potential to achieve high-speed and low-power spintronic memory, owing to the adaptive voltage modulated energy barrier of the MTJ. However, the three-terminal device structure needs two access transistors (one for write operation and the other one for read operation) and thus occupies larger bit-cell area compared to two terminal MTJs. A feasible method to reduce area overhead is to stack multiple VC-SOT MTJs on a common antiferromagnetic strip to share the write access transistors. In this structure, high density can be achieved. However, write and read operations face problems and the design space is not sure given a strip length. In this paper, we propose a synchronous two-step multi-bit write and symmetric read method by exploiting the selective VC-SOT driven MTJ switching mechanism. Then hybrid circuits are designed and evaluated based a physics-based VC-SOT MTJ model and a 40nm CMOS design-kit to show the feasibility and performance of our method. Our work enables high-density, low-power, high-speed voltage-control SOT memory.