A silicon micromachined microphone for fluid mechanics research

Abstract

MEMS piezoresistive sound detectors have been fabricated using the dissolved wafer process for the first time. The sensors utilize stress compensated PECVD ultra-thin silicon-nitride/oxide membrane together with monocrystalline ion-implanted p++ silicon piezoresistors to achieve high sensitivity. Tests reveal that sensors with a diaphragm size of 710 μm have a static sensitivity of 1.1 μV VPa−1 with 2% non-linearity over an operating pressure range of 10 kPa. This sensitivity is substantially larger than that of commercially available microfabricated sensors. Furthermore, the new sensor's dynamic response is found to be flat (within ±2.5 dB) over a frequency range extending up to 10 kHz. This paper contributes to existing literature in the field by demonstrating a new way of fabricating capable MEMS piezoresistive pressure sensors, hence adding to the overall versatility of the technology and associated range of applications.