Role of IrO₂ Electrode in Reducing the Retention Loss of Ir/IrO₂/Pb(Zr, Ti)O₃/Ir Capacitors

Abstract

Oxide electrodes are known to significantly improve reliability problems, such as fatigue and retention, in Pb(Zr, Ti)O₃(PZT)-based ferroelectric capacitors. To understand the roles of the oxide electrodes on the opposite-state retention, we investigated the isotope tracer experiments and hysteresis measurements on Ir/IrO₂/PZT/Ir and Ir/PZT/Ir capacitors before and after the retention tests. The depth profile of isotopic ¹⁸O in the Ir/IrO₂/PZT/Ir capacitor, measured by the second ion mass spectroscopy, shows little changes in the ¹⁸O and ¹⁶O distributions at the IrO₂/PZT interface. In addition, the hysteresis measurements showed that the internal field created by the retention tests should be nearly the same for both capacitors, indicating that the IrO₂ layer should not play an important role in compensating the interface defect charges (possibly, the oxygen vacancies).