A Novel STT-MRAM Cell With Disturbance-Free Read Operation

Abstract

This paper presents a three-terminal Magnetic Tunnel Junction (MTJ) and its associated two transistor cell structure for use as a Spin Torque Transfer Magnetoresistive Random Access Memory (STT-MRAM) cell. The proposed cell is shown to have guaranteed read-disturbance immunity; during a read operation, the net torque acting on the storage cell always acts in a direction to refresh the data stored in the cell. A simulation study is then performed to compare the merits of the proposed device against a conventional 1-Transistor-1-MTJ (1T1MTJ) cell, as well as a differential 2-Transistor 2-MTJ (2T2MTJ) cell. We also investigate In-Plane Anisotropy (IPA) and Perpendicular-to-Plane Anisotropy (PPA) versions of the proposed device. Simulation results confirm that the proposed device offers disturbance-free read operation while still offering significant performance advantages over the conventional 1T1MTJ cell in terms of average access time. The proposed cell also shows superior performance to the 2T2MTJ cell, particularly when the cells are targeted for read-mostly applications.