Electrode Dependent Thermal Stability of PZT Thin Film for Post-Piezoelectric Process

The thermal stability of piezoelectric properties of lead zirconate titanate (PZT) thin film is critical for its compatibility with typical MEMS fabrication process. In this study, we investigated the shifts in the piezoelectric and ferroelectric properties of PZT thin films with different top electrode materials after heating up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$450^{\circ}\mathrm{C}$</tex>, CMOS compatible process thermal budget. The measured <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$e_{31,f}$</tex> variation results demonstrate that PZT films with Pt electrodes maintain stable after heat treatment. In contrast, PZT films using Cr or Ti adhesion layers for the top electrode experience significant degradation, which is attributed to the oxidation of Cr and Ti, creating oxygen vacancies in the PZT films. Furthermore, the measured results of piezoelectric and polarization hysteresis loops demonstrate a strong correlation between piezoelectric and ferroelectric properties. This paper provides guidance and key insights for the development of high temperature post-piezoelectric MEMS process.