Influence of chemical corrosion on resistivity and 1/f noise of polysilicon gauges

Abstract New reliability problems rise for microsensors working in harsh environments: e.g., polycrystalline silicon piezoresistive gauges can be deteriorated in many applications, thus leading to a decrease of the sensor lifetime. In order to investigate these problems, polysilicon gauges highly doped with boron were processed, and accelerated corrosion tests were realized in different atmospheres. Two different runs were processed in order to distinguish the effect of corrosion on polysilicon only from the effect on the whole gauge. Electrical characterization of the gauges was then performed. The static characterization shows that only the thermal budget is responsible for the degradation of polysilicon resistivity. On the dynamic point of view, the 1/ f noise developed by the gauges was found to be very sensitive to the kind of atmosphere and also to the thermal budget. Chlorine reveals to be very corrosive for polysilicon even at only 5% mixture with air or argon. Kinetics of the chemical reactions seems to be attainable from 1/ f noise measurements.