MEMS惯性器件敏感电容结构相关温度漂移特性仿真

基于MEMS器件的微型惯导系统的精度和MEMS惯性器件的全温稳定性具有很高的相关性.MEMS结构相关的温度漂移主要来自材料之间的热失配应力,工艺引入的应力,以及封装应力等.而相关应力在MEMS结构中的分布以及所造成的应变又和MEMS结构具有一定相关性.通过ANSYS有限元分析软件建立了多种MEMS惯性器件常用梁-质量块结构的FEM模型,具体包括悬臂梁结构、双端固支梁结构、L形梁结构、对角支撑梁结构.通过热-力耦合仿真,研究了热失配应力在上述结构中的分布以及所产生的结构变形.对比分析了不同芯片粘胶形式,包括中心粘胶、三点粘胶、整片粘胶对上述MEMS结构引入的封装应力以及其全温(-40℃～60℃)温度漂移特性.此外,还分析研究了不同衬底厚度对MEMS结构封装应力的隔离效果.

Simulation research on structure-related thermal drifts of sensing capacitances of MEMS inertial sensors

The precision of the inertial navigation is highly related with the thermal stability of MEMS inertial sensor devices.The structure-related thermal drift is mainly caused by the mismatch stresses of MEMS material,the fabrication-induced stress,and the packaging stress.This paper focuses on the FEM simulation researches of standard bulk silicon MEMS inertial devices.Based on ANSYS FEM simulation,the FEM models of common beam-mass structures in MEMS inertial devices are built,including cantilever beam,double-clamped beams,L-shaped beams,and diagonal-suspension beams.Based on thermal-mechanical coupling simulation,the distributions of thermal mismatch stresses in these structures and the resulting structural deformation are studied.Based on the coupling simulation of multi-physics fields in full temperature range from-40℃ to 60℃,the packaging-induced stress and the stress-temperature relationship of various chip-bonding methods are evaluated,including single-point chip bonding,multi-points chip bonding,and whole area bonding.In addition,the isolation effects of different substrate thicknesses on the packaging-induced stress are shown by analysis and research.