A Study on a Sector-Shaped Cantilever Diaphragm for Frequency-Response Improvement of an Acoustic Sensor Based on Piezoresistive Effect in MOSFET.

This study investigates an acoustic sensor that exploits the piezoresistive effect of a field-effect transistor (PrFET) with a sector-shaped cantilever that improves frequency-response characteristics. PrFET energy transduction is capable of detecting acoustic signals by adopting an acoustically responsive sensing structure. However, it has not been investigated whether PrFET acoustic sensors can exhibit signal-response characteristics that differ from those previously reported. To investigate whether the sensor response could be enhanced at a specific frequency, this study adopted a sector-shaped cantilever diaphragm. The sector-shaped cantilever has a free end at the center, allowing for greater stress to be induced in the piezoresistive channel under acoustic excitation. The acousto-mechanical response of the proposed structure was characterized in terms of its displacement under acoustic excitation and the resulting stress induced in the PrFET at the support. A PrFET acoustic sensor incorporating the designed diaphragm was then fabricated, and the sensitivity enhancement and the formation of a specific resonance frequency was experimentally validated.