Influence of Glass-Frit Material Distribution on the Performance of Precision Piezoresistive MEMS Pressure Sensors

A microelectromechanical pressure sensor, including its vacuum reference cavity, has been modeled with focus on resulting stress from a glass-frit bonding process. Based on X-ray microtomography of bonded samples, a parametric model for the finite element analysis of variations in bonding material has been developed. The calculated influence on the sensor zero point and thermal coefficient of offset agrees well with measurements performed on various sensor variants. Signal changes during the first thermal cycles after glass-frit bonding were observed. We also observed the formation of microcracks in the excess glass-frit material during temperature cycling. The formation of these microcracks is shown to be a possible cause for the observed signal changes.