Mechanical-thermal noise characterization of a new micromachined acoustic sensor

B. Mezghani; F. Tounsi; M. Masmoudi

doi:10.1117/12.720185

11 June 2007 Mechanical-thermal noise characterization of a new micromachined acoustic sensor

B. Mezghani, F. Tounsi, M. Masmoudi

Proceedings Volume 6600, Noise and Fluctuations in Circuits, Devices, and Materials; 660015 (2007) https://doi.org/10.1117/12.720185
Event: SPIE Fourth International Symposium on Fluctuations and Noise, 2007, Florence, Italy

Abstract

A new integrated CMOS micromachined inductive microphone is studied and characterized for mechanical-thermal noise. This acoustic sensor has one suspended membrane attached to the substrate with 4 arms, the I-beam or L-beam shaped attachments. This membrane has 1.4x1.4mm² active area, 22&mgr;g mass and its natural frequency is found to be around 250 kHz, for the I-beam and 134 kHz, for the L-beam attachment. We give a brief explanation of the superiority of this new design over conventional acoustic sensors. Then, some experimental points are discussed and solutions are given. This sensor is analyzed for mechanical-thermal noise by applying a new developed analysis based on mass and natural frequency. Our system damping factor is found to be 5x10^-2 N.s.m^-1, which gives a fluctuating force spectral density of 2.88x10^-11 N.Hz^-1/2. This corresponds to an A-weighted sound level of about 39 dB(A) SPL. A SNR value of 55 dB is found for an incident pressure of 1 Pa on the suspended membrane. The relationship between the SNR and the mechanical and geometrical characteristics of the suspended membrane is also investigated. Finally, our sensor mechanical noise displacement is evaluated, around 10^-15 m.Hz^-1/2, and plotted for the two attachment types.

Citation Download Citation

B. Mezghani, F. Tounsi, and M. Masmoudi "Mechanical-thermal noise characterization of a new micromachined acoustic sensor", Proc. SPIE 6600, Noise and Fluctuations in Circuits, Devices, and Materials, 660015 (11 June 2007); https://doi.org/10.1117/12.720185

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