A silicon capacitive microphone based on oxidized porous silicon sacrificial technology

A new capacitive microphone fabrication technology is proposed. It uses oxidized porous silicon sacrificial technology to make air gaps and using KOH etching technique to make the backplate containing acoustic holes based on the principle that the heavily p⁺-doped silicon can be nearly etched in KOH solution. The innovation of the method is using oxidized porous silicon technology. The sensitivity of the fabricated microphone is from -55 dB (1.78 mV/Pa) to -45 dB (5.6 mV/Pa) in the frequency range of 500 Hz to 25 kHz. Its cut-off frequency is higher than 20 kHz.