Research On Design And Manufacturing Process Of Three-axis Fully Differential Capacitive MEMS Micro-accelerometer

MEMS is an interdisciplinary frontier subject developed on the basis of microelectronic technology.MEMS has been widely used in automotive electronics,smart phones,aerospace,national defense and military industry due to its small size,light weight,high integration,low energy consumption and high reliability.As one of the earliest research directions of MEMS sensors,MEMS micro accelerometer is the core component of inertial navigation,inertial guidance,seismic detection,automobile airbag and other systems.Compared with piezoresistive and heat flow micro-accelerometers,capacitive micro-accelerometers have higher accuracy,sensitivity and lower temperature coefficient.Combining the research background and current status of development,this dissertation takes the three-axis fully differential MEMS micro accelerometer as the research object,and studies the device design,model construction,structure simulation analysis and manufacturing process of the micro accelerometer.The specific research contents are as follows:Firstly,the MEMS technology and the application advantages of SOI wafer in the field of MEMS are introduced.Secondly,comparisons of different accelerometers with different sensing types are made.Then the development history and research status of MEMS micro accelerometer at home and abroad are introduced.Finally,the reason why the three-axis fully differential capacitive MEMS micro accelerometer is chosen as the research topic is explained,and the significance of choosing this research topic is explained.Then the basic working principle of capacitive micro accelerometer is analyzed theoretically.Secondly,by studying the sensitive mass,comb capacitance and elastic support beam of micro accelerometer,Tian shaped mass is selected as the sensitive mass,equal height comb capacitance of offset structure and equal height comb capacitance of uniform structure are selected as the comb capacitance,and trapezoidal beam is selected as the elastic support beam.Finally,the overall structure of the micro accelerometer is determined and the specific structure size is given.Then the finite element simulation software ANSYS is briefly introduced.The rationality of selecting trapezoidal beam is verified by using the simulation software,and the structure modeling,structure simulation and analysis of the designed micro accelerometer are carried out.The displacement sensitivity of x-axis,Y-axis and z-axis is 5.24×10^-5μm/g,5.54×10^-5μm/g,2.70×10^-4μm/g respectively.The measuring range is1000g,1000g and 200g respectively.The linearity is good and the maximum acceleration is 30000g,30000g and 3000g respectively.Through the dynamic simulation of the designed accelerometer structure,it is found that the resonance frequencies of X,Y and Z axes are quite different,and the order of magnitude is ten kilohertz,which indicates that the cross-axis interference of the designed accelerometer in the plane and vertical direction is small,and the resonance will not occur in the general working frequency range,which meets the design requirements.At last,on the basis of formulating the manufacturing process of the micro-accelerometer,the key process steps of the micro accelerometer are studied,and the appropriate process parameters are found out.