Self-Heating Analysis of MgO Spin-Transfer Torque Magnetic Tunnel Junctions: a Simulation Study

The high-current density prevalent during the operation of spin-transfer torque magnetic tunnel junctions (MTJs) causes significant self-heating, which invariably influences the endurance and reliability of these devices. In this work, based on numerical simulations, we present a theoretical study of self-heating taking into account the magnetic switching dynamics and three-dimensional heat transfer characteristics of STT-based MTJ devices. The impact of self-heating has been explored for different dimensions, geometrical aspects and bias conditions of the device. The temperature rise of the MTJ stack is observed to be strongly dependent on the choice of the encapsulating material and top metal layer thickness. Because of the asymmetry of the stack, device-to-device self-heating variability is expected to be larger in undercut structures than in the overcut ones. From transient analysis it is observed that during both unipolar and bipolar pulsing conditions, MRAM switching is accompanied by an abrupt change of temperature of around 25–30 K. The overall results of this work suggest that consideration of magnetic switching dynamics is essential to accurately estimate self-heating during transient and steady-state operations of STT-based MTJ devices.