High-Density and Low-Power Nonvolatile Static Random Access Memory Using Spin-Transfer-Torque Magnetic Tunnel Junction

Abstract

A novel nonvolatile static random access memory cell is proposed that consists of four transistors and two spin-transfer-torque magnetic tunnel junctions (STT-MTJs). In the case of the NFET driver cell, the free layers of the magnetic tunnel junctions are connected to the transistors' sources and drains to make the cell read-disturb free. The static power is totally eliminated as the power line is shut down during data hold. The static noise margin of the cell is calculated based on the experimental data on MTJ switching that is enhanced from the resistive load SRAM cell due to the MTJ's switching operation. The cell size is estimated to become smaller than the 6-transistor SRAM cell when it is designed at 45 nm node and beyond owing to the MTJ's area shrink as well as the thinning of its tunnel dielectrics (MgO).