Micromachined piezoelectric microphone with high signal to noise ratio

This paper reports on a micromachined microphone with high signal to noise ratio (around 60 dB). The microphone was fabricated by using sol-gel Pb(Zr,Ti)O
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thin film and silicon deep reactive ion etching technique. The core structure of the microphone is a circular clamped membrane consisting of a 2 μm-thick Si supporting layer and a 0.7 μm-thick PZT, which is fabricated on a siliconon-insulation wafer. The measured noise floor of the fabricated microphone is equivalent to 34 dB sound pressure level, indicating that the noise level of the piezoelectric microphone itself is not inherently high. The piezoelectric microphone can be used in audio frequency range by appropriately selecting a low noise preamplifier.