A high sensitivity polysilicon diaphragm condenser microphone

This paper presents the analysis, design, fabrication, and testing of a condenser microphone utilizing a thin low-stress polycrystalline silicon diaphragm suspended above a p+ perforated back plate. The microphone is fabricated using a combination of surface and bulk micromachining techniques in a single wafer process without the need of wafer bonding. The device shows sensitivities of -34 dB (ref. To 1 V/Pa) for 2 mm diaphragms with bias of 13 V and -37 dB for 2.6 mm-wide diaphragms at 10 V in good agreement with expected performance calculations.