Microstructure and properties of PbZr1-xTixO₃ thin films made by one and two step metalorganic chemical vapor deposition

Ferroelectric films of PbZr1-xTixO3 (PZT) have been prepared by one and two step MOCVD techniques using an advanced oxide MOCVD tool. The PZT films were deposited onto 6″ Pt/Ti/SiO2/Si and Si wafers to measure their phase formation, microstructure and ferroelectric properties. It was found that nucleation of the PZT perovskite phase started when the deposition temperature exceeded 550°C and grain growth dominated at 650°C and above. The grain size of PbZr0.5Ti0.5O3 thin films increased from 0.04 μm to 0.3 μm with increasing deposition temperature, but the surface roughness and leakage current also increased. Therefore, in order to obtain dense and homogeneous PZT films that have low surface roughness, we have developed a two step MOCVD process. The PZT thin films made by this two step MOCVD process exhibit excellent ferroelectric properties. Typically, 300 nm thick PZT films with a grain size about 0.3 μm have Pr greater than 20–30 μC/cm2 at 5V, a dielectric constant around 1000, and low coercive field (Ec 50–70 kV/cm), fatigue rate about 0.4 after 109 cycles at 5V and leakage current 2 × 10−7 A/cm2 at 100 kV/cm and room temperature on Pt electrodes. The microstructure and ferroelectric properties of PZT thin films made by both one and two step MOCVD techniques were also investigated.