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Electromagnetic Investigation of a CMOS MEMS Inductive Microphone

Auteur(s) : F. Tounsi, B. Mezghani, L. Rufer, M. Masmoudi, S. Mir

Journal : Sensors & Transducers Journal (ISSN 1726- 5479)

Volume : 108

Issue : 9

Pages : 40-53

This paper presents a detailed electromagnetic modeling for a new structure of a monolithic CMOS micromachined inductive microphone. We have shown, that the use of an alternative current (AC) in the primary fixed inductor results in a substantially higher induced voltage in the secondary inductor comparing to the case when a direct current (DC) is used. The expected increase of the induced voltage can be expressed by a voltage ratio of AC and DC solutions that is in the range of 3 to 6. A prototype fabrication of this microphone has been realized using a combination of standard CMOS 0.6 µm process with a CMOS-compatible post-process consisting in a bulk micromachining technology. The output voltage of the electrodynamic microphone that achieves the µV range can be increased by the use of the symmetric dual-layer spiral inductor structure.