Analysis of dielectric breakdown in CoFeB/MgO/CoFeB magnetic tunnel junction

The time-dependent dielectric breakdown has been investigated in a series of nominally identical Co–Fe–B/MgO/Co–Fe–B junctions by voltage ramp experiments. The results divulge that the breakdown voltage strongly depends on the polarity of the applied voltage, junction area, ramp speed and the annealing temperature. Magnetic tunnel junctions (MTJs) with positive bias on the top electrode show higher breakdown voltage than MTJs with negative bias. We found that there is a significant decrease in the breakdown voltage when the annealing temperature is increased above 350 °C. The experimental data can be described by different specific forms of breakdown probability functions which lead to different extrapolation of life time of junctions.