Leakage current conduction in IrO₂/PZT/Pt structures

Abstract

Over the last few years, thin films of PbZrxTi1 − xO3 (PZT) have been the focus of extensive researches for high-k capacitor applications. However, we believe that the reliability properties and the degradation mechanisms of PZT capacitors need to be better understood. A good way to learn about failure mechanisms is to investigate the characteristics of leakage current conduction. In this paper we propose a model for current density evolution of IrO2/PZT/Pt structures as a function of time, voltage and temperature. The voltage and temperature evolution of leakage current is interpreted as an interface controlled thermoionic injection of carriers over a potential barrier at the cathode/PZT contact. The time evolution of the leakage current is mainly characterized by the resistance degradation phenomenon which results in a large increase in current density. A quantitative analytical model based on the redistribution of oxygen vacancies near the cathode interface has already been developed to account for this effect [1]. We propose a more complete model that also includes the role of oxygen vacancies on dielectric relaxation and trapping phenomena. The contributions of Pt and IrO2 electrodes on leakage current evolution are also discussed.