Design and Simulation of Silicon Condenser Microphone for Industrial Use

摘要

A single-chip silicon condenser microphone with a sandwich diaphragm and an electroplating perforated copper backplate has been developed. Four edges of square sensing diaphragm are built in silicon substrate.The diaphragm consists of a heavily doped layer of polycrystalline silicon and two layers of silicon nitride.We adjust the thickness of three layers and select adapt MEMS fabrication process to have the sandwich diaphragm slight tensile The backplate is made using copper electroplating technology and perforated with circular holes. Perforated circular holes on backplate are laid out as hexagon to adjust air-gap damping between diaphragm and backplate to critical damping, which can increase resonant frequency of diaphragm and enlarge frequency bandwith of microphone. Fabrication is simple enough and only needs five photolithography marsks.Calculation and analysis show the open-circuit sensitivity with 9V bias voltage reaches 4.9mV/Pa, the pull-in voltage is 32.83V and the frequency bandwith ranges from 0 to 134KHz .Thereby, it can meet the demands of industrial use