Degradation in the ferroelectric and piezoelectric properties of Pb(Zr,Ti)O₃ thin films derived from a MEMS microfabrication process

We have investigated the influence of the microfabrication processes for microelectromechanical systems (MEMS) on the degradation in the ferroelectric and piezoelectric properties of Pb(Zr,Ti)O₃ (PZT) thin films. Multilayers of Pt/Ti/PZT/Pt/Ti/SiO₂ were deposited on silicon-on-insulator (SOI) wafers. The multilayers were fabricated into piezoelectric micro cantilevers through a MEMS microfabrication process. The positive and negative remanent polarizations were reduced to 56% and 35% of the initial value after the microfabrication process. The results indicated that the top interface between PZT and Pt sustained more damage than the bottom interface. We have also found that wet etching of PZT thin films especially degrades the ferroelectric property. The butterfly curve for the displacement of the fabricated cantilevers displayed an asymmetric shape. This reflects the greater damage to the top interface between the PZT and Pt thin films. The transverse piezoelectric constant, d₃₁, of the PZT thin films is estimated to be -72 pm V^-1.