CONTRIBUTION OF ELECTRODES AND MICROSTRUCTURES TO THE ELECTRICAL-PROPERTIES OF PB(ZR0.53TI0.47)O-3 THIN-FILM CAPACITORS

Pb(Zr0.53Ti0.47)O-3 (PZT) thin film capacitors have been fabricated with four electrode combinations: Pt/PZT/Pt/SiO2/Si, 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/cm(2) at 1 V) irrespective of the top electrode material. Capacitors with Pt bottom electrodes have much lower leakage currents (J = 10(-8) A/cm(2) 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.