Soft breakdown in MgO dielectric layers

In this work, we report on the occurrence of the soft breakdown (SBD) failure mode in 20 nm-thick films of magnesium oxide (MgO) grown on Si substrates. To our knowledge, this is the first observation of this failure mechanism in a high-kappa gate dielectric with such a large oxide thickness. We show that the I-V characteristics follow the power-law dependence typical of SBD conduction in a wider voltage range than that reported for SiO₂. We pay special attention to the relationship between the magnitude of the current and the normalized differential conductance, and analyze the role played by the injection polarity and substrate type.