Theoretical and numerical modeling of a CMOS micromachined acoustic sensor

Abstract

In this paper, we present theoretical and numerical modeling done on a new structure of CMOS micromachined inductive microphone. Its mode of operation is based on the variation of the mutual inductance between an external fixed inductor and an internal suspended inductor. This internal inductor is designed on a 1.4timesl.4mm2 suspended membrane. The displacement of the suspended membrane with two different attachment structures, the I-shaped and the L-shaped beams, is studied, losing a theoretical mechanical modeling, we get displacement values of 13.11 mum and 68.82 mum, for the I-shaped and L-shaped beam design, respectively. With a numerical FEM analysis, using the Ansys software, displacement values of 12.7 mum and 63.5 mum were found for the I-shaped and L-shaped beam design, respectively. Using the analogy between acoustic, mechanical and electrical domains, the dynamic behavior of the L-shaped beam design sensor is studied and a corner frequency around 200 kHz is found. This value is also found when applying analytical dynamics principles to determine the equations of motion for the suspended membrane. A FEM analysis, using the Ansys software, is conducted in order to validate this theoretical model