Evaluation of PZT capacitors with Pt/SrRuO3 electrodes for FeRAM

(Pb,La)(Zr,Ti)O-3 [PLZT] films were prepared by CSD on sputtered electrodes of Pt/IrO2 on SiO2/Si wafers. Top electrodes consisting of Pt/SrRuO3(SRO) were sputter deposited and the Pt/SRO/PLZT/Pt capacitors were annealed at 600 degrees C. Evaluation of fatigue endurance revealed that more than 6% excess Pb was necessary to produce a fatigue free:capacitor. However, the FeCap leakage current increased in proportion to the film excess Pb content. SIMS analysis of the FeCap containing 10% excess Pb revealed that Sr from the 70 nm thick SRO electrode diffused into the PLZT film to the bottom electrode during,the anneal resulting in high leakage, FeCap leakage current was greatly reduced by decreasing the PLZT film excess Pb content and SRO film thickness. SRO electrodes with thicknesses of 5 and 15 nm were found to be sufficient to produce a capacitor with high Fatigue endurance and little static imprint. These results indicate that the PLZT leakage current was greatly influenced by the Sr interdiffusion and reaction with excess Pb to form a grain boundary conduction phase, SrPbO3. By optimizing process conditions, a low leakage, high endurance FeCap consisting of Pt/SRO/PLZT/Pt was produced.