Contribution of electrodes and microstructures to the electrical properties of Pb(Zr_0.53Ti_0.47)O₃ thin film capacitors

Pb(Zr_0.53Ti_0.47)O₃ (PZT) thin film capacitors have been fabricated with four electrode combinations: Pt/PZT/Pt/SiO₂Si, RuO₂/PZT/Pt/SiO₂/Si, RuO₂/PZT/RuO₂/SiO₂/Si, and Pt/PZT/RuO₂/SiO₂/Si. It is shown that polarization fatigue is determined largely by the electrode type (Pt vs RuO₂), and microstructure has only a second-order effect on fatigue. If either the top or bottom electrode is platinum, significant polarization fatigue occurs. Fatigue-free capacitors are obtained only when both electrodes are RuO₂. In contrast, the bottom electrode is found to have a major effect on the leakage characteristics of the PZT capacitors, presumably via microstructural modifications. Capacitors with bottom RuO₂ electrodes show high leakage currents (J = 10⁻³-10⁻⁵ A/cm² at 1 V) irrespective of the top electrode material. Capacitors with Pt bottom electrodes have much lower leakage currents (J = 10⁻⁸ A/cm² at 1 V) irrespective of the top electrode material. At low voltage, the I-V curves show ohmic behavior and negligible polarity dependence for all capacitor types. At higher voltages, the leakage current is probably Schottky emission controlled for the capacitors with Pt bottom electrodes.