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J.N. Haus, M. Schwerter, M. Schneider, M. Gäding, M. Leester-Schädel, U. Schmid, A. Dietzel:
"Robust Pressure Sensor in SOI Technology with Butterfly Wiring for Airfoil Integration";
Sensors, 21 (2021), 6140; 1 - 12.

Current research in the field of aviation considers actively controlled high-lift structures
for future civil airplanes. Therefore, pressure data must be acquired from the airfoil surface without
influencing the flow due to sensor application. For experiments in the wind and water tunnel,
as well as for the actual application, the requirements for the quality of the airfoil surface are
demanding. Consequently, a new class of sensors is required, which can be flush-integrated into
the airfoil surface, may be used under wet conditions-even under water-and should withstand
the harsh environment of a high-lift scenario. A new miniature silicon on insulator (SOI)-based
MEMS pressure sensor, which allows integration into airfoils in a flip-chip configuration, is presented.
An internal, highly doped silicon wiring with "butterfly" geometry combined with through glass
via (TGV) technology enables a watertight and application-suitable chip-scale-package (CSP). The
chips were produced by reliable batch microfabrication including femtosecond laser processes at
the wafer-level. Sensor characterization demonstrates a high resolution of 38 mV V−1 bar−1. The
stepless ultra-smooth and electrically passivated sensor surface can be coated with thin surface
protection layers to further enhance robustness against harsh environments. Accordingly, protective
coatings of amorphous hydrogenated silicon nitride (a-SiN:H) and amorphous hydrogenated silicon
carbide (a-SiC:H) were investigated in experiments simulating environments with high-velocity
impacting particles. Topographic damage quantification demonstrates the superior robustness of
a-SiC:H coatings and validates their applicability to future sensors.

http://dx.doi.org/10.3390/s21186140