CMOS integrated micromachined inductive microphone

Abstract

A novel silicon micromachined inductive microphone has been proposed, designed and analyzed. The microphone is fabricated on a single wafer by the use of bulk micromachining technology that is post-processing on substrates containing integrated circuits (IC's), independently of the IC process. The working principle of this pressure sensor is based on inductance coupling between an external fixed inductor and an internal suspended inductor. Due to mutual inductance effect on vibrating the internal inductor, we obtain a varying voltage proportional to the amplitude variation of the incident wave. This internal inductor is designed on a 4-lever double turn suspended membrane. When compared with the single turn structure, it is found to be much more flexible. For the double turn structure, we intend to make a study of the variation of the mutual inductance and its derivative under the effect of two main factors. The first factor to study be the number of turns in the secondary and the primary inductors, which we choose to be the same. The suspended membrane dimensions constitute the second factor to study. We notice that the first factor has a bigger effect on the mutual inductance and on the output voltage.