Design and analysis of a silicon condenser microphone

Abstract

The design and analysis of a capacitive microphone is presented in this paper. Capacitive microphone with considerably higher sensitivity and low power consumption offers the innovative design for sound pressure microsensors. Polysilicon with smooth surfaces and incredible low residue stress is used for diaphragm of the capacitive microphone. Two methods—equivalent circuit method and finite element method—have been applied in this research to achieve the highest sensitivity of capacitive microphone. Optimal diaphragm edge width, thickness, and air gap have been determined through analyzing and simulating sound pressure microsensors, understanding the variation of geometry dimensions parameters between diaphragm and air gap distance, and dissecting the impact among sensitivity, nature frequency and electric field. Consequently, the valuable design model is able to be provided for the best choice of sound pressure microsensors among different materials. In addition, the results can improve and control the performance and dimensions of this microsensor. Furthermore, the microphone is fabricated using a combination of surface and bulk micromaching techniques which has favorable integrated capability of CMOS (Complementary Metal-Oxide Semiconductor). These device and techniques are promising for the future production.