A simple four-point-bending setup for measurement of mechanical stress on silicon field-effect transistors

A simple four-point-bending setup integrated with a foil strain gauge is presented for the direct measurement of mechanical stress (MS) on metal–oxide–semiconductor field-effect transistors (MOSFETs). The magnitude of the external MS applied to MOSFETs can be directly obtained through the resistance change due to strain in the strain gauge mounted on the wafer strip. Then the resistance change in the strain gauge is detected in a Wheatstone quarter-bridge circuit. In addition, the validity of the direct stress measurement is confirmed by using the finite element analysis. Finally, through the direct stress measurement on MOSFETs, the longitudinal piezoresistance coefficients appear to be fairly comparable with the reported values in earlier literatures. The stress measurement is also expected to be applicable to the evaluation of uniaxial-process-induced strained MOSFETs.