Research On Capacitor Fringing Effect And Structure Anti-interference Of Nano-g Accelerometer

In the fields of geophysics,gravitational wave detection and planetary gravity detection,the nano-g level resolution of accelerometers is required.At present,in the research of improving the resolution and other performance of accelerometers at home and abroad,the sensor gain is mainly increased by optimizing the mechanical structure,and the low noise circuit is developed to improve the signal-to-noise ratio.Among them,MEMS capacitive micro accelerometer is an important part of high-precision acceleration detection due to its skilled processing technology and strong environmental adaptability.This paper has studied the key structure and key technology of MEMS micro capacitive accelerometer,and designed an accelerometer with nano-g level thermal and strong antiinterference ability.At the same time,the influence of fringing effect on the sensitivity of array capacitance is studied.Finally,the preparation technology of accelerometer is studied and the processing map of each layer is drawn.The main work of this paper is as follows:(1)The fringing effect model is proposed by inheriting the traditional models and modifying them based on conformal mapping transformation and complex function correlation theory.Compared with the traditional models,the proposed model is better because the error between the proposed model and the finite element simulation,which is from 10% to 20% when the capacitor plate is moved from perfectly aligned to completely misaligned,is less than that between the traditional models.In addition,by analyzing the attenuation mechanism of the sensitivity of capacitor array,the attenuation coefficient of its sensitivity under different plate spacing is obtained.(2)Based on the theory of fluctuation dissipation of damping system,the mathematical thermal noise model of spring-vibrator structure is established.The mechanical structure with theoretical mechanical thermal noise of 0.1ng/√Hz is obtained by parametric modeling of the spring-vibration structure,which indicates that the resolution of the accelerometer reaches the level of nano-g.(3)By studying the coupling model of frame,a combination model of local coupling and frame drilling is proposed,which effectively reduces the influence of interference acceleration on the sensitivity of array capacitance.The theoretical rang of the final accelerometer is greater than ±2g,and the model frequency ratio between the non-detected direction and the detected direction of the structure is greater than 7.49.(4)By exploring the MEMS processing technology,according to the structural characteristics of the designed accelerometer,the preparation technology was determined,and L-edit was used to draw the layout of each layer.