Design and characterization of a micro strain gauge

Silicon piezoresistive stress sensors are used to measure stress on a plastic-encapsulated silicon die. These sensors are conventionally fabricated onto the surface of silicon integrated circuit die as part of the normal processing procedure. Since they can also be used over a wide temperature range after calibration, thermally-induced stresses can be measured. A four-point bending (4PB) stress fixture was used in calibration experiments. The results between the four-point resistance measurement and two-point resistance measurement of the strain gauges were compared. The problem in the calibration process was discussed.