A Miniature Condenser Microphone for Portable Terminals Applications

This paper presents a miniature condenser microphone with a flexure hinge diaphragm for portable terminals applications. MEMS technology has been successfully applied to miniature silicon capacitive microphones, and we fabricated the smallest condenser silicon microphone in the presented reports. We used the finite-element analysis (FEA) to evaluate mechanical and acoustic performances of the condenser microphone with a flexure hinge diaphragm. From the simulation results, we confirmed that the sensitivity of a flexure hinge diaphragm can be improved about 285 times higher than a flat diaphragm. The first and second modes occurred at 15,637 Hz and 24,387 Hz, respectively. The areas of the miniature condenser microphones with a hinge diaphragm are 1.5 mm times 1.5 mm. We measured the impedance characteristics and sensitivities of the fabricated condenser microphones. The sensitivities of microphones are around 12.87 muV/Pa (-60 dB ref. 12.5 mV/Pa) at 1 kHz under a low bias voltage of 1 V, and the frequency response is flat up to 13 kHz.