High-Performance Condenser Microphone With Single-Crystalline Silicon Diaphragm and Backplate

Abstract

This paper presents a high-performance silicon condenser microphone fabricated with a new process using single-crystalline silicon. This simple fabrication process, which requires only two photolithography steps and two wet-etching steps, is suitable for low-cost mass production. We designed the structure of a high-performance microphone and simulated it with an equivalent acoustic-circuit model. We then fabricated a prototype microphone based on this design, and experimental measurements on the prototype confirmed its excellent acoustic characteristics, such as a high sensitivity of -43.5 dB, a wide frequency range of 30 Hz to 20 kHz, and a high maximum sound pressure level (1 kHz at 1% THD) of 122 dB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SPL</sub> . The measured equivalent noise (A-weighted) is 30.5 dBA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SPL</sub> . The measured frequency responses showed good agreement with those estimated from the simulation, indicating that the high controllability of the process enabled us to fabricate the prototype as we designed it. These results show that it is feasible to economically mass produce such high-performance microphones for purposes ranging from broadcasting to consumer use