Miniature condenser microphone with a thin silicon membrane fabricated on SIMOX substrate

A new condenser microphone with a 300 nm thick monocrystalline silicon and silicon nitride sandwich diaphragm and an aluminium backplate fabricated using a sacrificial resist layer, is presented and tested. Microphones with diaphragm side lengths of 200 to 476 µm show a flat frequency response between 50 Hz and 20 kHz and sensitivities up to 0,35 mV/Pa at bias voltage of 2V. The microphones can be fabricated on a single wafer without bonding techniques. The technology is suitable for integration of a CMOS signal processing electronic circuit.