Structure and dynamic characteristics of silicon condenser micromachined microphone

Design and dynamic analysis of a single-chip silicon condenser micromachined microphone were presented for micromachined microphone industrial batch-production.Two electrodes of the condenser micromachined microphone were formed by a sandwich sensing diaphragm and a copper backplate.The gap between the diaphragm and backplate was formed by the sacrificial technology.The sandwich diaphragm was fabricated using low-pressure chemical vapor deposition(LPCVD).It was composed of a heavily boron doped layer of polycrystalline silicon and two layers of silicon nitride.The backplate was fabricated using copper electroplating technology and perforated with circular holes.Perforated circular holes on backplate were laid out as hexagon.Perforated circular holes can adjust air damping between the diaphragm and backplate to critical damping.Analysis and calculation showed that the microphone had the open-circuit sensitivity of 4.99 mV/Pa at the bias voltage of 9 V,the pull-in voltage was 32.83 V,and the working frequency bandwidth ranged from 0 to 134 kHz.