High-temperature polysilicon pressure microsensor

A thin-film polysilicon on insulator microsensor for low-pressure/high-temperature measurements has been developed. The microsensor is constituted by a micromachined silicon diaphragm, a thin silicon dioxide layer, an optimized sputtered boron-doped polysilicon layer, photolithographically patterned on a Wheatstone bridge configuration, and an aluminium interconnection layer. The complete fabrication process is described. The sensors manufactured in this way exhibit low temperature coefficients of resistance and sensitivity over the range 25–250 °C and a good long-term stability. The sensitivities measured are up to 3 mV V⁻¹ bar⁻¹. The deviation from linearity and hysteresis observed in the output characteristics is measured in the pressure range 0–10 bar.