International audienceThis paper describes the conception, designs consideration and fabrication process of a novel MEMS microphone. The presented microphone not only uses a new architecture, the sensitive part being beams moving within the plane of the substrate, but also uses an innovative detection means with Silicon piezo-resistive nanogauges. Modelization will consider acoustic and mechanical interactions. Besides, at MEMS scale, accurate simulation of the sensor must take into account thermal and viscous boundary layers in acoustics, and we will show that the presented sensor takes benefit from these short scale effects, which leads to achieve theoretical resolution as low as 24dB
To cite this version:Thierry Verdot, Emmanuel Redon, Kerem Ege, Jaroslaw Czarny, Cécile Guianvarc'H, et al.. Microphone with planar nano-gauge detection: fluid-structure coupling including thermoviscous effects. Acta Acustica united with Acustica, Hirzel Verlag, 2016, 102 (3)
AbstractThis article presents the modeling of a MEMS microphone with an original architecture formed of mechanical structures moving in the plane of the substrate. On the contrary of most microphones generally constituted of an oscillating membrane, some transducers developed by the CEA-LETI with M&NEMS technology use micro beams moving in the plane of the silicon wafer under the effect of an acoustical wave. These micro-structures are connected to the substrate by flexible micro-hinge and strain silicon nano-gauge producing a variation in resistance by piezoresistive effect. After the description of the design and functioning of the microphone under study, the vibroacoustic model of the fluid-structure coupling is presented. Considering the dimensions of the MEMS transducer close to the thermal and viscous boundary layers thicknesses, this model has to include diffusion phenomena. The model is discretized using the finite element method and the weak formulation is implemented using COMSOL Multiphysics® software. The pressure sensitivity of the microphone is calculated and compared with an analytical lumped model to asses the numerical model. Pressure and velocity fileds are also computed. Solutions of simulations are interpreted by focusing on phenomena influencing the sensitivity of this novel sensor design. In particular, the influence of the geometry and the role of the different part of the transducer (back cavity, mechanical structures) are studied.
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