A Low Temperature Prepared MEMS Microphone with High Sensitivity
ZHANG Zhongshan;TANG Liang;Institute of Acoustics,Chinese,Academy of Sciences;
MEMS Microphone is the sensor converting the sound signal into the electrical signal. At present,the researches of MEMS Microphone mainly refer to condenser microphone,piezoelectric microphone and piezoresistive microphone. Compared with the other MEMS microphone,MEMS condenser microphone possesses prominent advantages of high sensitivity,high signal to noise ratio( SNR),flat frequency response and low temperature coefficients,which is widely applied in portable device,multimedia equipment,hearing-aid,information acquisition. A MEMS condenser microphone with high sensitivity is designed and prepared at temperature of less than 300° C which is compatible with IC processing. The method of sacrificial layer is used to develop the circular vibrating membrane which avoids stress concentration question in quadrangular membrane,which overcomes expensive dry etching.Based on polyimide material and optimized processing parameters of membrane preparation,low stress circular membrane is developed. The question of film adhesion in release process is avoided by designing anti-adhesive structure.According to the theoretical computation,the capacitance change of the device with the stress in vibrating membrane of 5 MPa,the radius of 2.5 mm,the thickness of 1 um and the electrode radius is thousandth at 1 Pa sound pressure.Compared with MEMS microphone being sold,the above capacitance change is an order of magnitude larger than that. The MEMS condenser microphone in this paper can be applied in far-field pickup that picking important sound signal from low SNR circumstance.
【CateGory Index】： TN641