A silicon subminiature microphone based on piezoresistive polysilicon strain gauges

Abstract A silicon subminiature microphone, based on the piezoresistive effect in polysilicon using only one chip, is proposed. The acoustic sensor is fabricated by a technique that is compatible with a slightly modified CMOS process also using a standard micromechanical fabrication technology. The main production steps will be described, including the design and the fabrication of the sensor. Experimental results of the piezoresistive coupling factors and the temperature dependence of the polysilicon resistors are given. Measured results of the airborne sound sensitivity are about −92 dB/Pa. The frequency response is nearly flat with deviations of about ± 3 dB from 100 Hz to 5 kHz and with a resonance at 10 kHz.