Sensitivity-improved silicon cantilever microphone for acousto-optical detection

Silicon cantilever sensors have been designed, fabricated and tested in acoustic wave detection. The principal application of the components is photoacoustic spectroscopy (PAS) which is a highly sensitive method in solid, liquid and gas analysis. The developed microfabrication process of the sensors is based on silicon-on-insulator (SOI) wafer etching, in which the challenge is to control and minimize the residual stress related curving in thin (5 μm) but large-area (few mm2) components. The sensitivity of the fabricated cantilevers is investigated in photoacoustic measurements of solid samples, and the signal strength is shown to increase tens of percent compared with the results obtained with previously reported cantilever microphones. Improvement of the signal-to-noise ratio (SNR) verifies the advantage of the presented cantilevers in photoacoustic sensing.