Calibration considerations for piezoresistive-based stress sensors

The authors present a study of the variation of the piezoresistive coefficients over several devices on the same die, the same wafer, and at different doping levels. The sensor test vehicles are fully documented, and a thorough error analysis on the method of applying a known uniaxial state of stress is presented. It is shown that individual stress-sensor calibration is required if the uncertainty in the absolute values of the measured stresses needs to be less than 15%. If the uncertainty only needs to be less than 50%, then one device per wafer can be calibrated or an equation relating the unstressed resistance values to the piezoresistance coefficients can be used