Effect of the Porosity of PZT Thick Films on Mass Sensitivity and Resonance Force for Cantilever Type Bio Sensors

PZT thick films fabricated through the screen printing show a porosity ranging from 20% to 40%. Unfortunately, these high porosities of thick films greatly affect electromechanical characteristics of PZT thick film cantilevers. In this paper, we report a systematic analysis regarding the effect of the thick film porosity on the electromechanical characteristics of the PZT thick film cantilever. PZT (Pb(Zr₀.₅₂Ti₀.₄₈)O₃) thick film cantilever devices were successfully fabricated on a Pt/Ti₀₂/SiNx/Si substrate using a screen printing method and MEMS processes. Theoretical calculations of mass sensitivity and actuating force of PZT thick film cantilevers are presented with respect to material properties (density and Young´s modulus) and geometry (length, width, and thickness) of PZT thick films, which are dependent on experimentally verified material and geometrical parameters. From the result of modeling, it is confirmed that the increase of Young´s modulus due to the decrease of porosity of PZT thick films is more efficient than the control of the cantilever geometry, for increasing the cantilever resonating force. On the other hand, the optimization of geometric constituents is more effective than the control of densification of PZT thick films, for increasing the cantilever sensitivity.