Piston-type condenser microphone with structured polysilicon

A miniature silicon condenser microphone with a reinforced piston type diaphragm has been developed. The microphone, with a highly sensitive diaphragm (1mm2 in area) and a highly rigid back plate has been fabricated in a single wafer process. The equivalent electrical circuit method and the finite element method (FEM) have been used to evaluate the acoustic and mechanical performance of the microsensor. A procedure to achieve a structure with optimal mechanical sensitivity has been proposed and diaphragms with different geometries have been designed and simulated with this method. Sensitivities in the range of 5 - 10 mVPa-1 can be achieved under bias voltages of 1.5 - 7 V for devices with frequency bandwidths between 10 and 50 kHz