Fabrication and electromechanical properties of piezoelectric micro-transducers for smart device

We have fabricated piezoelectrically driven micro-transducer for the application to smart device. Two types of micro-transducers, i.e., micro-cantilever and micro-bridge, have been designed and fabricated. Finite element method (FEM) simulation was performed on the micro-transducer with various length and shapes. Lead zirconate titanate thin film as a piezoelectric layer was incorporated into the micro-transducer. The transducer structure consists of PZT thin layer capacitor, low temperature oxide (LTO) and low stress SiN_x layer. Pb(Zr_0.52Ti_0.48)O₃ (PZT) films were prepared by diol-based sol-gel process. The PZT films were not damaged by fabrication process and thus maintained their electrical properties in the transducer structure after all the fabrication steps. The dielectric constant and loss of the PZT film in the transducer structure were 870 and 1% respectively. The remanent polarization was 20 μC/cm². The micro-cantilever had a fundamental resonant frequency in the range of 16 to 25 kHz when its length was in the range of 320 μm to 380 μm. Meanwhile, the resonant frequency of the micro-bridge was higher by a factor of 7 than that of the micro-cantilever with a similar dimension.