Effects of the structural layer in MEMS substrates on mechanical and electrical properties of Pb(Zr0.52Ti0.48)O3 films

In this paper, we describe the effects of the structural layer in substrates on the mechanical and electrical properties of Pb(Zr0.52Ti0.48)O3 (PZT) films for MEMS applications. The PZT films were deposited by a sol–gel method on platinized silicon substrates where silicon nitride and silicon oxide were used as a structural layer. The mechanical properties of PZT films were characterized by nanoindentation. The ferroelectric and dielectric properties as a function of film thickness and layer material were investigated. Residual stresses in PZT films were also characterized by Raman spectroscopy. The measured mechanical properties of PZT films on two types of substrate indicate that the structural layer has significant influence on the obtained indentation moduli of PZT films. The PZT on SiNx-based substrates, i.e., PZT//SiNx/Si multilayer structure presented higher measured values than those of PZT on SiO2-based substrate, i.e., PZT//SiO2/Si multilayer structure throughout the whole indentation depth. The substrate effect on film hardness, however, was negligible since hardness value of around 8.8 GPa was measured for both PZT on SiNx and SiO2-based substrates. Significant influences of the film thickness and substrate type on the electrical properties were not observed for the investigated thickness range of the PZT films.