Design and fabrication of piezoresistive p-SOI Wheatstone bridges for high-temperature applications

Julian Kähler; Lutz Döring; Stephan Merzsch; Andrej Stranz; Andreas Waag; Erwin Peiner

doi:10.1117/12.886855

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5 May 2011 Design and fabrication of piezoresistive p-SOI Wheatstone bridges for high-temperature applications

Julian Kähler, Lutz Döring, Stephan Merzsch, Andrej Stranz, Andreas Waag, Erwin Peiner

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Proceedings Volume 8066, Smart Sensors, Actuators, and MEMS V; 806603 (2011) https://doi.org/10.1117/12.886855
Event: SPIE Microtechnologies, 2011, Prague, Czech Republic

Abstract

For future measurements while depth drilling, commercial sensors are required for a temperature range from -40 up to 300 °C. Conventional piezoresistive silicon sensors cannot be used at higher temperatures due to an exponential increase of leakage currents which results in a drop of the bridge voltage. A well-known procedure to expand the temperature range of silicon sensors and to reduce leakage currents is to employ Silicon-On-Insulator (SOI) instead of standard wafer material. Diffused resistors can be operated up to 200 °C, but show the same problems beyond due to leakage of the p-njunction. Our approach is to use p-SOI where resistors as well as interconnects are defined by etching down to the oxide layer. Leakage is suppressed and the temperature dependence of the bridges is very low (TCR = (2.6 ± 0.1) μV/K@1 mA up to 400 °C). The design and process flow will be presented in detail. The characteristics of Wheatstone bridges made of silicon, n- SOI, and p-SOI will be shown for temperatures up to 300 °C. Besides, thermal FEM-simulations will be described revealing the effect of stress between silicon and the silicon-oxide layer during temperature cycling.

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Julian Kähler, Lutz Döring, Stephan Merzsch, Andrej Stranz, Andreas Waag, and Erwin Peiner "Design and fabrication of piezoresistive p-SOI Wheatstone bridges for high-temperature applications", Proc. SPIE 8066, Smart Sensors, Actuators, and MEMS V, 806603 (5 May 2011); https://doi.org/10.1117/12.886855

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