Research On Characteristics Of Capacitive Silicon Microphone

In recent years,Micro-Electro-Mechanical Systems(MEMS)have been developed rapidly,especially MEMS microphones.And the market of MEMS microphones has grown exponentially with the widespread popularity of smart interactive devices.MEMS microphones have been commercialized on a large scale after more than 30 years of development,and are gradually replacing the status of electret microphones.At present,although there are many research institutions on MEMS microphones in China,most manufacturers just carry out packaging work without the core technology of MEMS chips.So,the study on the MEMS microphone is of far-reaching significance.In this paper,the characteristics of capacitive MEMS microphones are studied,and the realization process of MEMS microphones are elaborated around the aspects of simulation analysis,process design,process fabrication and package testing.First of all,the basic structure and size of MEMS microphone is optimized by the finite element simulation software(COMSOL).After the simulation optimization and model establishment of MEMS microphone are completed,the process flow is designed and the manufacturing of MEMS microphone is started in ultra-clean room.In the process,the fabrication of polysilicon films,the blister defects after the annealing of amorphous silicon films,the stress problem of films and the release of sacrificial layer were solved by experiments.Then,the test platform is built after the MEMS microphone is completed,and the electrical and acoustic characteristics of the MEMS microphone are studied.The innovation in this paper is to optimize the fabrication process of polysilicon film and the cavity release process in MEMS microphone.In addition,the blister prediction model and the method of microporous etching locally are proposed in the research of blister defects to prevent the amorphous silicon film from generating blister defects after annealing.The MEMS microphone chip designed in this paper has a size of 1.2mm×1.2mm×0.3mm,the sensitivity of the finished MEMS microphone is-38 dBV with a flatter frequency response,and the signal-to-noise ratio is 61 dBA with less than 0.5% of total harmonic distortion.What’s more,The MEMS microphone studied in this paper further improve the ability of MEMS chip manufacturing,and benefits the development of ultrahigh-performance MEMS microphones.