CMOS-Based Wheatstone Bridge Stress Sensors Sensitive and Insensitive to Mechanical Stress

This paper analyses the sensitivity of the pMOS Wheatstone bridge stress sensors in 180-nm CMOS process. Other reported works use coarser process nodes. The pMOS sensors have a maximum or minimum sensitivity to the in-plane normal stress components for different orientations of the bridge arms with respect to the wafer coordinate system. The experimental results show that the sensors oriented orthogonally to the wafer axes have an absolute sensitivity of around 400 µV/MPa, while the absolute sensitivity of the diagonally oriented sensors is around 3 µV/MPa. The temperature measurements show low temperature dependency. The sensitivity to stress changes around −3% at 5 °C and around +1% at 50 °C, with respect to 25 °C.