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

• We measure endurance of MgO based magnetic tunnel junctions in pulsed conditions.
• An optimum endurance is obtained for 100 ns delay between pulses.
• We model this behavior with electron trapping/detrapping on MgO barrier defects.
• Our model agrees with data and predicts high endurance in operating conditions.
• Low frequency noise and endurance of unexercised junctions are correlated.

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.