Design and characterization of a high sensitive MEMS capacitive microphone using coupled membrane structure

The micro scale high sensitive coupled membrane (HSCM) microphone has been reported in this paper and theoretically investigated. Membrane is one of the most important parts in micro electro mechanical microphones (MEMS microphone). In MEMS microphones, acoustic wave caused the membrane to deflect and become closer to the backplate. This deflection makes the surface of the membrane closer to the back plate and changes the capacity of the capacitor. This change is the main detection mechanism, used in the capacitive microphones (condenser microphones). Deflection of the membrane, caused its effective surface to decrease which negatively affects the sensitivity. Here, a design has been proposed to solve this problem and enhance the sensitivity of the microphone. In this design a special coupled diaphragm includes the two parts has been used. The first part is exposed to the acoustic wave and the second part, considered to be the moving electrode of the capacitor, is attached to the center of the first one, by means of an interface. This design provides the same deflection while keeps the effective surface unchanged.