Robust Pressure Sensor in SOI Technology with Butterfly Wiring for Airfoil Integration

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 mVV−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.

Электронно-пучковая кристаллизация тонких пленок аморфного субоксида кремния

Polycrystalline silicon (poly-Si) has been obtained for the first time as a result of an electron beam irradiation of amorphous hydrogenated silicon suboxide films with a stoichiometric coefficient of 0.5 (a-SiO0.5:H) and a thickness of 580 nm. The accelerating voltage of the electron beam was 2000 V, and the beam current was 100 mA. Raman spectra of silicon films after annealing are obtained depending on the time of electron beam irradiation of the initial material. It is shown that as a result of annealing, poly-Si is formed, the stress in which varied from compression to tension depending on the time of exposure.

Density of Defect States and Spectra of Defect Absorption in a-Si:H

Spectral characteristics of the coefficient of defect absorption in amorphous hydrogenated silicon have been studied. The characteristics are determined, by analyzing the electron transitions occurring with the participation of the energy states of dangling bonds. It is shown that the principal role in the formation of the defect absorption coefficient value is played by the electron transitions between defect and non-localized states. It is also shown that the spectral characteristics are mainly determined by the distribution function of the electron density of states in the valence or conduction band. It is found that the maxima in the spectrum of the defect absorption coefficient are observed only if there are pronounced maxima in the density of states at the edges of allowed bands.