Fabrication of microchannel and diaphragm for a MEMS acoustic sensor using wet etching technique

This paper reports a new technique for fabrication of diaphragm and microchannel in a single step for the development of a piezoelectric MEMS acoustic sensor. It describes the design of the sensor based on ZnO to be utilized for aero-acoustic measurements. A primary requirement for such devices is a high maximum sound pressure level [(SPL) similar to 180 dB] and flat frequency response in the audio band (20 Hz - 20 kHz). The Si-diaphragm thickness was optimized for the desired SPL range using Coventorware. The complete frequency response of the structure was determined using analytical formulations based on lumped element modeling (LEM). The fabricated device was tested using Laser Doppler Vibrometer (LDV). The lower cut-off frequency, bandwidth, resonance frequency and flat band sensitivity of the optimized device have been found to be 26.3 Hz, 40.0 kHz, 78.688 kHz and 148 mu V/Pa respectively.