Design and Fabrication of Piezoelectric MEMS Sensor for Acoustic Measurements

This study illustrates the design, modeling and fabrication of a piezoelectric acoustic sensor based on ZnO to be utilized for aeroacoustic measurements. In aeroacoustics, measurement of high sound pressure level (SPL) (upto similar to 180 dB) is a necessary prerequisite. The design of the device was accomplished through a combination of piezoelectric composite plate theory, lumped element modeling (LEM) and MEMS-CAD tool Coventorware. The optimization of Si-diaphragm thickness of the device for the desired SPL range was achieved by using Coventorware. Also, the cavity created after diaphragm development was connected to the outside environment via a microtunnel which was designed for low cut-off frequency. The complete frequency response of the device was determined from LEM using the simulation tool MATLAB. The low cut-off frequency, bandwidth and flat band sensitivity of the sensor have been found to be 48 Hz, 54 kHz and 130 mu V/Pa respectively. The designed sensor was fabricated using standard Si-fabrication technology. The testing of the fabricated device was done using Laser Doppler Vibrometer (LDV). The resonance frequency obtained from LDV measurement has been found to be 99.6 kHz.