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In this paper, we study by numerical and graphical modeling the electro-thermal behavior of heavily p-doped (N A =5×10 19 cm -3 ) suspended silicon nanowires for large self-heating. Computed results are correlated with experimental ones for top-down fabricated nanowires. The computed temperature rise along a Si nanowire due to Joule effect exhibits a complex nonlinearity for large biasing current when the thermal dependence of silicon nanowire properties is considered. The agreement with experimental results is improved by taking into account thermal conductivity variation resulting from size effects. The proposed model also enables a graphical interpretation of the hysteretic behavior of the silicon nanowire self-heating. Complementary phenomena and possible application are eventually discussed. [ABSTRACT FROM AUTHOR]

Abstract: A low cost and low temperature transfer process of electroplated Ni microstructures is presented. The process is based on adhesion control of molded Ni microstructures on donor wafer by using plasma deposited fluorocarbon film. Low temperature adhesive bonding of the microstructures on the target wafer using BCB sealing enables mechanical tear out from the donor wafer. Interest of this process is demonstrated here in the case of micro pressure sensors based on the Pirani principle. Suspended Ni electroplated microwires of 0.55 to 1.2 length, 10 μm width and 700 nm to 10 μm thickness were characterized into pressure dependant chamber. These sensors exhibit good sensitivity in the range of 0.1 to 100 mbar. The presented results thus demonstrate the interest of a simple film transfer process for elaboration of 3D microstructures. [ABSTRACT FROM AUTHOR]

Titanium, zirconium, and Zr-Ti alloy thin films were evaporated under UHV. AFM, TEM and SEM observations showed that grain size at the surface of the films varies with their thickness and composition. The single-metal films exhibit larger grain than alloy films. The highest density of grain boundaries is found for Zr-Ti film with a balanced content in Zr and Ti. For the three types of films, the grain boundary density at the surface decreases when increasing the film thickness. The gettering properties of the films were studied by activation annealing in the range of 200 °C–400 °C by in situ sheet resistance monitoring and by integrating them into MEMS packages sealed at 300 °C. In both cases, the sorption of gases was found to increase with the surface density of grain boundaries. In the specific activation conditions of MEMS packaging, it is shown that reducing the film thickness from 400 nm to 50 nm enhances gas sorption by the Zr-Ti getter and for the first time, the activation of a getter film thinner than 100 nm integrated in a MEMS package was demonstrated. • The single-metal films Zr and Ti have a lower grain boundary density than the Zr-Ti alloy films. • The higher grain boundary density is found for a Zr-Ti film having a balanced content in Zr and Ti. • Zr, Ti and Zr-Ti films exhibit a grain boundary density at the surface that decreases with film growth. • The film gas sorption is correlated with its surface grain boundary density. • Reducing the Zr-Ti getter film thickness from 400 nm to 50 nm can enhance its gas sorption capability. [ABSTRACT FROM AUTHOR]

We investigated the sorption of hydrogen by yttrium-based getters for their application to vacuum wafer-level packaging of microelectromechanical systems. Thin alloy films were co-evaporated under ultra-high vacuum on silicon wafers. Getters were activated by annealing during 1 h under inert argon atmosphere with traces of oxidizing species, at temperatures ranging from 200 °C to 400 °C. Three complementary techniques of ion beam analysis were performed on the samples: Rutherford Backscattering Spectrometry (RBS), Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA), to quantify metal, oxygen and hydrogen contents, and their in-depth distributions. The results show that oxidation occurs during annealing and prevents or not hydrogen sorption depending on the film composition. Due to its fast diffusion, hydrogen tends to accumulate near the film/substrate interface and starts to diffuse into the substrate as well. The different compositions of getter films are compared in terms of oxygen and hydrogen absorptions. • Y, Y–Al, Y–Ti, Y–V, Y–V–Al and Y–Zr–Al getter films were annealed under argon to simulate activation during a vacuum packaging process. • Oxygen and hydrogen contents were measured on the samples before and after annealing by RBS, NRA and ERDA. • Oxidation occurred during activation annealing and prevented or not hydrogen sorption, depending on the film composition. • Hydrogen tend to accumulate near the film/substrate interface in annealed films and start to diffuse into the substrate. [ABSTRACT FROM AUTHOR]