Resistivity dependence of gauge factor of polysilicon strain gauge

A method to estimate the gauge factor of a polysilicon strain gauge at the wafer level is proposed. It is difficult to measure the gauge factor of a polysilicon strain gauge formed on the silicon diaphragm of a mechanical transducer because the polysilicon strain gauge is integrated into the diaphragm. The authors fabricated polysilicon strain gauges of various shapes and implanted with various concentrations of boron, and measured the gauge factor of each strain gauge. In the experimental results, the gauge factors are calculated by multiplying the resistivity coefficient of gauge factor (RCGF) determined by the boron concentration and resistivity of the polysilicon strain gauge. The authors also determined the RCGF of the polysilicon strain gauges implanted with boron concentrations of 1.0×1019, 1.5×1019 and 1.0×1020 cm−3.