Pulse-Width and Temperature Effect on the Switching Behavior of an Etch-Stop-on-MgO-Barrier Spin-Orbit Torque MRAM Cell

In this letter, we present a novel step spin-orbit torque magnetic random access memory (SOT-MRAM) cell structure and its switching behavior. A special stop-on-MgO etch etches away the hard mask and the pinned layer while retaining the free layer (FL) and MgO as part of the cell. The extended Ta/CoFeB/MgO layer is proved to be more tolerant to the etching non-uniformity of the Ta nanowire and improve etching yield. Although etching stops on MgO, the FL underneath the thin MgO has been rendered nonmagnetic by the etching process. Recessed Cu pads were added to the Ta nanowire, which substantially reduces the overall resistance of the Ta nanowire. The general switching behavior of the step SOT-MRAM cells, such as pulse-width and temperature dependence of the switching currents, resembles that of a spin-transfer torque MRAM cell.