Fabrication and electromechanical properties of Pb(Zr_0.52, Ti_0.48)O₃ micro-diaphragm

Multilayered piezoelectric micro-diaphragms have been successfully fabricated by micro-electro-mechanical-system (MEMS) processing. The micro-diaphragms consisted of diol based sol-gel derived Pb(Zr _0.52Ti_0.48)O₃ (PZT) capacitor, sputtered Pt electrode, and low temperature oxide(LTO)/SiN_x/Si substrate. The PZT film exhibited (111) oriented structure. The dielectric constant and loss of the PZT thin films were 800 and 3% at 100-100 kHz, respectively. The remanent polarization was 20 μC/cm². The lateral dimension of the PZT film was varied relative to the square-shaped supporting membrane with 300 or 400 μm length. The relative size (ratio of lateral dimensions) of the PZT film to the supporting membrane was varied from 0.7 to 1.1 to investigate its influence on the system performance. The micro-diaphragm exhibited mechanical displacement from 0.067 to 0.135 μm at 15 V and had a maximum displacement at a ratio of relative size of 0.8, regardless of the lateral size of the supporting membrane. The fundamental resonant frequency of the micro-diaphragm which has 300 μm length supporting membrane was in the range of 348 kHz to 365 kHz, depending on the relative size. As the PZT size increased relative to the supporting membrane, the resonant frequency decreased and reached a minimum at the relative size of 0.8. The micro-diaphragm with the supporting membrane (400 μm length) had a lower resonant frequency, i.e., 251-270 kHz, but showed a similar behavior to the micro-diaphragm with the supporting membrane (300 μm length) in relation to the resonant frequencies with the relative size.