Reliability and properties of PZT thin films for MEMS applications

Thin films of PZT have been deposited using a solution deposition method onto platinized silicon substrates. The effects of process variables, including sintering time and solution molarity, have been investigated on the resulting microstructure and electrical properties. As utilizing piezoelectric thin films in geometries for MEMS applications requires load to be transferred between the film and an underlying membrane, the adhesion of these films has been examined using nanoindentation techniques. Delaminations occur at the PZT-Pt interface, suggesting that these films may be susceptible to interfacial failure with repeated bending. Longer firing times are shown to improve the adhesion of the films, but increase the surface roughness and grain size. Film hardnesses range between 4 and 6.8 GPa; for sintering times beyond 5 minutes at 700 degrees C the hardness appears relatively constant. Electrical properties are shown to degrade with tine at elevated temperatures.