Stress and Deformation Mechanics Model of Sensing Structure in Micro-Machined Capacitive SOI Accelerometer

Abstract

Due to the micro-machined processes, there is residual stress in device layer of capacitive SOI accelerometer, which results in the deformation in sensing structure and hence, makes the device fail to work. To cope with the problem, based on the stress and stress gradient in device layer, in light of the mechanics theory and by dividing the proof -mass into several continuous varied cross-section beams, utilizing symmetric continuous conditions and deformation compatibility, a stress and deformation mechanics model of sensing structure in SOI accelerometer is proposed. By the comparison between the model and experiment data, which is obtained SOI device layer 50 μm and oxide layer 5 μm and model, it is indicated that the model could basically describe the sensing structure deformation. The model could hopefully be helpful in further exploration on stress and deformation in MEMS structure.