一种用于MEMS超低值封装残余应力的测量方法

微机电系统(MEMS)封装残余应力是在封装工艺过程中芯片上产生的残余应力，它对于MEMS器件的热稳定性和长期贮存稳定性有着十分重大的影响，故而对MEMS封装残余应力的高精确度测量有利于封装应力的研究。由于封装残余应力十分微小，因此无法利用目前的测量手段直接测量封装应力，本文针对这个问题提出了一种基于应力放大结构和拉曼光谱法的封装应力测量方法，可以测量出MEMS器件中封装应力的平均水平。基于理论分析建立了原始封装模型与应力放大结构之间的放大关系，并提出应力放大结构的设计原则。接着采用3D有限元(FEM)仿真对一款高精确度MEMS微加速度计的封装应力测量进行了分析，其结果与理论分析具有很高吻合度。最后，针对该微加速度计的封装应力测量，成功制作了应力放大结构的芯片样片，并进行封装，随后拉曼光谱法被用于测量样片中的最大应力，进而计算出待测微加速度计中平均封装应力大小。实验结果与仿真分析具有很好的吻合度，证明本文所提出的测量方法具有相当的可靠性。

A novel measurement method of ultra-low residual stress in MEMS package

Micro-Electro-Mechanical System(MEMS) packaging stress is a residual stress produced by MEMS packaging process, which has significant influence on the thermal stability and long-term stability of MEMS devices. An accurate assessment of stress is useful for the studying of packaging stress. Because the package stress is too low to be directly measured by the existing techniques, a novel measurement method based on stress magnifying structure and micro-Raman spectroscopy is proposed to obtain the average package residual stress in MEMS devices. Based on the theoretical analysis, the magnification ratio between the original package model and the stress magnifying structure is obtained, and a design rule of the stress magnifying structure is given. Then, a Finite Element Modeling(FEM) of a kind of high precise MEMS micro-accelerometer is conducted to prove the theoretical analysis result. Finally, for the package residual stress measurement of the micro-accelerometer, fabrication and package are successfully performed. Then stress measurement experiment is conducted to measure the magnified package stress and to calculate the actual average package residual stress in the micro-accelerometer, showing an identical result with previous simulation, which proves the measurement method much reliable.