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Proceedings Paper

Design and fabrication of piezoresistive p-SOI Wheatstone bridges for high-temperature applications
Author(s): Julian Kähler; Lutz Döring; Stephan Merzsch; Andrej Stranz; Andreas Waag; Erwin Peiner
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Paper 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.

Paper Details

Date Published: 5 May 2011
PDF: 8 pages
Proc. SPIE 8066, Smart Sensors, Actuators, and MEMS V, 806603 (5 May 2011); doi: 10.1117/12.886855
Show Author Affiliations
Julian Kähler, Technische Univ. Braunschweig (Germany)
Lutz Döring, Physikalisch-Technische Bundesanstalt (Germany)
Stephan Merzsch, Technische Univ. Braunschweig (Germany)
Andrej Stranz, Technische Univ. Braunschweig (Germany)
Andreas Waag, Technische Univ. Braunschweig (Germany)
Erwin Peiner, Technische Univ. Braunschweig (Germany)


Published in SPIE Proceedings Vol. 8066:
Smart Sensors, Actuators, and MEMS V
Ulrich Schmid; José Luis Sánchez-Rojas; Monika Leester-Schaedel, Editor(s)

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