Fabrication and performance of a flat piezoelectric cantilever obtained using a sol-gel derived PZT thick film deposited on a SOI wafer

The present paper reports on the fabrication and performance of flat piezoelectric cantilevers obtained using a sol-gel derived PZT thick film deposited on a SOI (semiconductor-on-insulator) wafer. Highly (100) oriented PZT thick films (2.7 νm) have been deposited onto the SOI wafer with a Pt/Ti layer and an SiO₂ layer (Pt/Ti/SiO₂/Si/SiO₂/Si multi-layered structure hereafter) by the sol-gel technique. The upper SiO ₂ layer between the Pt/Ti bottom electrode and upper Si layer was found to play an important role in avoiding breaking the Pt/Ti bottom electrode. The dielectric constant and the remanant polarization of the deposited PZT films were measured as 1250 and 17 νC cm^-2 respectively. The transverse piezoelectric constant (-d₃₁) estimated from these data is 117 pC N^-1. After coating the Pt/Ti top electrode on the PZT layer, microfabrication techniques were used on the Pt/Ti/PZT/Pt/Ti/SiO ₂/Si/SiO₂/Si multi-layered structures to form piezoelectric cantilevers. The resulting cantilevers composed of Pt/Ti/PZT/Pt/Ti/SiO₂/Si multi-layered structures were found to be flat. The transverse piezoelectric constant (-d₃₁) of the PZT thick films calculated from the measured displacement of the cantilevers is 84-132 pC N^-1. The present data are 4-5 times larger than our previous data. This may be due to low stress in the PZT thick film achieved by using the Si layer of the Pt/Ti/SiO₂/Si/SiO₂/Si multi-layered structure as a structural material.