Analysis and simulation of the post-breakdown leakage current in electrically stressed TiO2/SiO2 gate stacks

The post-breakdown leakage current in electrically stressed metal-oxide-semiconductor structures with thin stacked layers of titanium dioxide (TiO2) over silicon dioxide (SiO2) was investigated. The samples were obtained by plasma oxidation at room temperature. Multiple dielectric breakdowns were induced by the application of successive high-field voltage ramps. The resulting current–voltage characteristics were simulated using an equivalent electrical circuit model consisting in a diode with series and parallel resistances, which is solved using the Lambert W function. We show that after the first breakdown event the current that flows through the non-damaged gate stack area may still play a major role in determining the shape of the post-breakdown current–voltage characteristic. Similarities and differences with previous studied systems are discussed.