Design and modeling of a ZnO-based MEMS acoustic sensor for aeroacoustic and audio applications

Abstract

In previous research work related to the acoustic sensors, the researchers had focused on the individuality of the sensors for aeroacoustic application and sensors for audio range application. This paper describes a simple and novel model of acoustic sensor for aeroacoustic and audio applications (microphone). The model of the device presented in this paper shows interoperability. The sensor reported has the bandwidth of~22 KHz, which covers the entire bandwidth of microphone and aeroacoustic sensors. A LEM (Lumped Element Model) is used to determine the characteristics of the device. The device has the square diaphragm of 1.5 × 1.5 mm2 and a nominal thickness of 15 μm to sustain the high SPL (Sound Pressure Level). A piezoelectric ZnO layer 2.4 μm-thick is sandwiched between two Al-top and bottom electrodes. The top electrode is segmented to enhance the sensitivity of the device. Furthermore, a microtunnel of 100 μm wide and 21μm deep is designed to achieve the lower cut-on frequency of ~5 Hz. The theoritical results show that the sensor has sensitivity (RMS) of 126.3μV/Pa and 96.6 μV/Pa in case of central and outer electrodes respectively. The resonant frequency of ~ 85 KHz is obtained from lumped model, simulated using MULTISIM 13.0. The result is verified with MEMS-CAD TOOL COVENTORWARE®.