Aluminum Induced Crystallization of <italic>In-Situ</italic> Phosphorus Doped E-Beam Evaporated Silicon Films for High Gauge Factor Piezo-Resistors

A polysilicon film with high gauge factor formed at a low thermal budget of 450 °C is reported in this paper. The polysilicon was formed using in-situ phosphorus doped ultra-high vacuum e-beam evaporated amorphous silicon film as a precursor for aluminum induced crystallization (AIC). The crystallization, electrical and piezo-resistive properties of the resulting films for various phosphorus doping levels have been studied. The results show that the gauge factor of the AIC polysilicon film increases with phosphorous doping level of the precursor. The reduction in doping concentration and formation of large grains with average size of 8.77 μm have allowed a gauge factor of 77 to be at obtained with phosphorus doping of 2 × 1019cm-3in the precursor. This, to our knowledge, is the highest gauge factor reported for polysilicon and may lead to post-CMOS monolithic integration of high performance strain sensors.