Acoustic analysis and fabrication of microelectromechanical system capacitive microphones

Abstract

This paper presents a microelectromechanical system (MEMS) capacitive microphone fabricated by using a combination of surface and bulk micromachining techniques equipped with favorable integrated complementary metal-oxide semiconductor capability. Through the proposed equivalent circuit model for the packaged microphone, optimal diaphragm diameter, diaphragm thickness, backplate height, air gap, front chamber volume, back chamber height, and acoustic hole fraction have been determined by analyzing and simulating the capacitive microphone. Consequently, this design model can optimize choice of materials, microphone size, and microphone performance. All parameters for the analysis have been experimentally measured for the microphone. To verify our analysis, the microphone sensitivity has been experimentally measured by pulse electroacoustics with the software SOUND CHECK in an anechoic box. The simulation and experimental results for sensitivity of the microphone follow each other within a range of 2 dB. Moreover, the measured specifications indicate that the packaged microphone has notably high sensitivity (−42±3 dB V/Pa at 1 kHz), low power consumption (<250 μA), high S/N ratio (>55), and low distortion (<0.5%).