Current Instability, Permittivity Variation With Frequency, and Their Relationship in Ta2O5 Capacitor

In this paper, Ta₂O₅ current instability in MIM and MIS capacitors is studied over several sample thicknesses with a current-versus-time measurement and low-frequency dielectric spectroscopy. Three types of phenomena are identified. The first one is attributed to polarization current correlated to flat loss behavior. The second mechanism corresponds to the conduction current identified as a steady state: a unique mechanism, probably a Poole-Frenkel one, is observed on the whole investigated voltage range. Finally, a resistance degradation phenomenon occurs that has been attributed to ionic diffusion in dielectric and follows the space-charge-limited theory. According to physical characterization, a model based on oxygen vacancies migration in the dielectric is suggested. Moreover, according to low-frequency dielectric spectroscopy measurements, it has been identified that the low-frequency loss peak is created by the same defects and is well modeled by the Maxwell-Wagner approach.