Silicon piezoresistive stress sensors can be used for in-situ stress measurements of the encapsulated silicon die. These sensors are fabricated using conventional integrated circuit technology as part of the normal silicon processing process. Since they can also be used over a wide temperature range after calibration, the thermally induced stresses can be measured. In this thesis, the theoretical background of micro strain gauge stress sensors was reviewed. The design consideration of the stress sensors and the design parameters of two kinds of stress sensors were presented. The micro strain gauges were calibrated using a four-point bending fixture. The error associated with this calibration method was studied. The resistance of the micro strain gauge was found to vary linearly with the...[ Read more ]

Silicon piezoresistive stress sensors can be used for in-situ stress measurements of the encapsulated silicon die. These sensors are fabricated using conventional integrated circuit technology as part of the normal silicon processing process. Since they can also be used over a wide temperature range after calibration, the thermally induced stresses can be measured. In this thesis, the theoretical background of micro strain gauge stress sensors was reviewed. The design consideration of the stress sensors and the design parameters of two kinds of stress sensors were presented. The micro strain gauges were calibrated using a four-point bending fixture. The error associated with this calibration method was studied. The resistance of the micro strain gauge was found to vary linearly with the applied stress and the temperature. The piezoresistive coefficients were calculated and found to be in agreement with the reported values for silicon. The problems associated with the calibration process were also discussed. Finally, the micro-strain gauge stress sensors were encapsulated using a standard PQFP (Plastic Quad Flat Pack) package. The resultant stress was measured. We found the magnitude of the measured stress was in the range predicted by the simulations. However, there was also some differences between the simulations and the measured results.