High sensitivity silicon-based condenser microphone design

An innovative design of high sensitivity capacitive microphone is described in this paper. The condenser microphone is made by micro-electro-mechanical systems (MEMS) fabrication technology. The advantages of MEMS microphone are small size and low cost. Besides, surface mount technology (SMT) compatible is an important reason for application. Basic structures of the silicon condenser microphone include a highly sensitive poly-silicon membrane and a rigid monocrystalline silicon counter electrode with acoustic holes on it. Optimized membrane design called bridge structure achieves the goal of stress release in thin-film process. The thickness of membrane is 3 um and the air gap between membrane and backplate is 3 um as well. Proposed microphone design can reach 14.21 mV/Pa open-loop sensitivity with bias voltage 8.17 V. The natural frequency of the device is 25.8 kHz.