Breakdown mechanisms in MgO based magnetic tunnel junctions and correlation with low frequency noise

Magnetic tunnel junctions (MTJs) are very attractive for magnetic random access memories (MRAMs), thanks to their combination of non-volatility, speed, low power and endurance. In particular spin transfer torque (STT) RAMs based on STT writing show a very good downsize scalability. However, an issue is that at each write event, the MTJ is submitted to an important electrical stress due to write voltage of the order of half of the electrical breakdown voltage. Here we present a study of breakdown mechanisms in MgO based MTJ performed under pulsed conditions. We developed a model of charge trapping/detrapping on barrier defects to explain and predict device endurance. We also show that endurance is correlated to low frequency 1/f noise and that such noise measurement could thus be used as a non destructive and predictive tool for the reliability of the devices.