Study On Key Technology Of Optical Interferometric MEMS Microphone

Microphone is a kind of acoustic sensor which can collect natural acoustical signals.It has important application value in military,aerospace,medical,consumer electronics,automobile electronics and other fields.Therefore,it is of great significance to study the microphone.The traditional capacitive MEMS microphone is the most widely used technology in the field of consumer electronics.However,due to its own design conflicts,it cannot simultaneously meet the requirements of higher sensitivity,signal-to-noise ratio or larger working bandwidth.Optical interferometric microphones offer possibilities for this purpose,and microphones based on Fabry-Perot interferometers,Mach-Zehnder interferometers,Sagnac interferometers,and Fizeau interferometers have been published and have achieved high sensitivity and SNR.However,most of the optical interference microphones are designed as optical fiber sensors,which are difficult to manufacture,have poor repeatability and high cost.MEMS technology has the advantages of high reliability,low manufacturing cost and mass production,so optical interferometric microphone based on MEMS is an ideal design method.However,there are few researches in this field.Therefore,this paper proposes a MEMS microphone design based on optical interference principle,and carries out systematic research on it.The main contents are as follows:Firstly,the paper analyzes and studies the acoustic sensing technology based on different structures,and makes clear the structural advantages of MEMS microphone with optical interference.The development,process and application of MEMS technology are introduced,which provides theoretical support for MEMS technology to be applied in the production of microphone.Secondly,the structure of the sensor is designed,and the double layer structure of the backplane including the micro grating is determined.The preliminary simulation is carried out to determine the size parameters,and the finite element simulation of the resonant mode is carried out to ensure that it can work normally within the required bandwidth.In addition,the manufacturing process of microphone device is deeply studied and analyzed,and the overall technological process of making the device is introduced in detail.Some technological steps are optimized and improved,so that the sensor has better consistency and reliability in the manufacturing process.Finally,the effect of optical interference MEMS microphone is verified and a sensor testing system is built.The time domain response characteristics,linear response characteristics,frequency domain response characteristics,signal-to-noise ratio,consistency and other important parameters of the sensor are studied.The future improvement direction of the sensor is also considered.Due to the limitation of process conditions and the room for further improvement of structural design,device design needs to be optimized to further improve the performance.But this work provides a new idea for the research of optical microphone and lays a foundation for the future development of the design.