Design and Simulation of PZT-based MEMS Piezoelectric Sensors

Devices with increased sensitivities are needed for various applications including the detection of chemical and biological agents. This paper presents the design of microelectromechanical systems (MEMS) devices that incorporate lead zirconate titanate (PZT) films in order to realize highly sensitive sensors. In this work, the piezoelectric properties of the PZT are exploited to produce sensors that perform optimally for mass sensing applications. The sensor is designed to operate as a thin-film bulk acoustic resonator (TFBAR) whereas a piezoelectric is sandwiched between electrodes and senses a change in mass by measuring a change in resonance frequency. Modeling of the TFBAR sensor, using finite element analysis software COMSOL, was performed to examine optimal device design parameters and is presented in this paper. The effect of the PZT thickness on device resonance is also presented. The piezoelectric properties of the PZT is based on its crystal structure, therefore, optimization of the PZT film growth parameters is also described in this work. A detailed description of the fabrication process flow developed based on the optimization of the device design and film growth is also given. The TFBAR sensor consists of 150 nm of PZT, 150nm of silicon dioxide, silicon substrate, titanium/platinum bottom electrodes, and aluminum top electrodes. The top electrodes are segmented to increase the sensitivity of the sensor. The resonance frequency of the device is 3.2 GHz.