Design and implementation of a novel double-poly microphone with rigid acoustic receiver, flexible spring supporter, and harm backplate

This study reports the design and implementation of a novel micromachined microphone. The design of the microphone is based on the well-known two-poly processes. The design as shown in Fig.1 has four merits, (1) rigid-diaphragm formed by the rib-reinforced poly-Si as acoustic wave receiver and moving-electrodes, (2) flexible-spring formed by thin poly-Si as diaphragm supporter, (3) rigid-diaphragm anchored to flexible-spring by central poly-via, and (4) very rigid plate formed by high-aspect-ratio (HARM) trench-refilled poly-Si as stationary-electrodes and back-plate. To demonstrate the feasibility, the two-poly microphone has been implemented and tested. Typical measurement results show that the sensitivity of microphone is 12.63 mV/Pa (-37.97 dB/Pa) measured at the sound level of 94 dB.