Silicon subminiature microphones with organic piezoelectric layers: fabrication and acoustical behaviour

A silicon subminiature microphone, based on the piezoelectric effect of organic films such as aromatic polyurea, PVDF, and P(VDF/TrFE) (polyvinylidene fluoride/trifluoroethylene) is proposed. The acoustical sensor is fabricated using a slightly modified integrated circuit technology process and a standard micromechanical fabrication procedure. The main production steps of this 'hybrid' sensor are described, including the fabrication of the mechanical part of the sensor, the deposition or spin coating of the films, and the poling of the polymer layers. Measurements of the transverse piezoelectric charge constant d/sub 31/ and results of this sensitivity to airborne sound of the aromatic polyurea microphones are presented. >