Characterization of two novel low frequency microphones for photoacoustic gas sensors

The photoacoustic principle for measuring gas concentration is well established based upon macromechanical assembly. However, microsystem based photoacoustic could benefit from smaller size and lower cost, but needs a high resolution microphone to be competitive. Here we present the characterization of two dedicated low frequency microphones. Both microphones have been fabricated in the same MPW foundry process, but additional post processing step enabling narrow ventilation slots through membranes of multiple thickness that increase the sensitivity of microphones, has been used. Preliminary results indicate a sensitivity of 800 μV/V-Pa, sufficient for high resolution photoacoustic gas sensors.