A SOI sandwich differential capacitance accelerometer with low-stress package

Thermal stress and device bending have significant effect on the performance of MEMS sensors. In this paper, a MEMS sandwich differential capacitance accelerometer with low-stress package is presented. The accelerometer is based on a thin silicon middle layer which has been bonded with two glass electrode plates. A metal hermetic package case is used for reliability and noise immunity. The purpose is to simplify manufacturing process and reduce thermal influence. The methods of reducing thermal stress and deflection were evaluated. The thickness of glass electrode plates was optimized for low-stress. A silicon multi-point supporting frame which could reduce thermal stress between glass electrode plate and metal case was designed and simulated. The stress model in this study provides useful information for sandwich structures. Test results in actual device show it has the sensitivity of 0.1124V/g and 0.435% nonlinearity error in test range of 0~50g, 0.02%/°C zero temperature drift without temperature compensation.