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The sol–gel coating method is considered to be simple and easy to implement to lead to organic/inorganic hybrid coatings. In addition, the application of thin films by this technique is inexpensive and applicable on large substrates without form restriction. In this context, thin sol–gel coatings based on a mixture of three alkoxysilanes and synthesized in purely aqueous phase with different thicknesses and with the presence or not of ZrO2 nanoparticles, were applied on metallic and glass substrates. After application and curing, the mechanical properties of sol–gel coatings were characterized by Berkovich nanoindentation with continuous stiffness measurement mode (CSM). The effective elastic moduli as well as the hardness values were estimated for each coating along the indentation depth and as a function of the substrate material and sol–gel characteristics. The effect of a annealing at higher temperature was also studied. Then, the failure modes of sol–gel coatings were investigated using both Berkovich nanoindentation and nanoscratch technique with a 5 µm radius spherical diamond tip. Careful microscopic observations of residual imprints and residual grooves both exhibit chipping in case of thick coating especially on glass substrate and no dramatic failure for thin coating applied on both substrates. It is shown in this work that the mechanical properties of the sol–gel and the mechanical stability of coatings on substrates are influenced dramatically by the presence of nanoparticles and the thermal treatment. Finally, interfacial fracture toughness of sol–gel coatings on substrate was estimated using analytical model from the literature and Ashby map based on experimental results was created using performance indices in order to proceed to sol–gel coating selection.

Cadmium coatings are used in aerospace and offshore industries for parts in corrosive environments. Since cadmium is a highly toxic heavy metal, it is subject to strong restrictions. Alternatives include Al-based alloys. The present work describes preliminary results for Cd substitution by using Al-Mn with 25 at.-% Mn deposited on 42CrMo4 steel by atmospheric plasma spraying (APS). The prepared alloy powder for the APS process was characterized by laser granulometry, SEM/EDX, and STA. A fraction with particle sizes ranging from 20 µm to 45 µm was used for the thermal spraying process. The APS coating and an Al reference sample were characterized by image analysis, Vickers hardness, and Standard Salt Spray (SSP) testing. The Al-Mn coating exhibits a significantly higher hardness in comparison to pure Al. In both cases, red iron corrosion did not appear during SSP testing. The Al coating was partially covered by a thick oxide film, whereas Al-Mn showed only moderate oxidation but lower adhesion to the substrate

Low temperature direct bonding has been used extensively for assembling materials or components in the microelectronics and microsystem industries. We review here some key features of this technique both from the experimental and practical point of views. We give also some indications on the physical and chemical mechanisms involved in this attractive process, to better identify the important parameters impacting the quality and reliability of the technique. We describe mechanisms and report results on Si and SiO2 bonding processes. Emphasis is put on improvements that allow obtaining strong and high quality bonding in low temperature process. We demonstrate that direct bonding can be applied as well to metal bonding, mainly to obtain conductive bonding, provided an efficient process can be used for surface preparation, e.g. CMP smoothing. More generally we show that direct bonding is well suited for many heterostructures via low temperature process for instance.

Direct silicon or silicon dioxide wafer bonding appears as a more and more attractive way to build up stacking structures in micro-technologies. For this, high bond strengths and void-free bonding interfaces are required. Although Si-Si hydrophilic bonding provides suitable bonding energies after low temperature annealing (T

CEA-INAC, 17, rue des Martyrs 38054 GRENOBLE - France Low temperature wafer bonding is requested in many applications. Most of them involve silicon or silicon dioxide bonding interfaces. Studying bonding process / mechanism in the low temperature range (

Direct silicon wafer bonding is an attractive way to build up stacked structures. For applications, defect free bonding is required whatever the post bonding processes, which can include thermal treatment. Direct bonding processes are usually applied with hydrophilic surfaces. Thus water trapped at bonding interfaces can induce low temperature oxidation, which is a source of gas and bonding defects. The aim of this paper is to compare the efficiency of various H2O diffusion barriers, which can be elaborated onto silicon wafers before bonding. Behaviors of thin thermal silicon oxide, thermal silicon nitride and plasma induced silicon oxynitride capping layers have been evaluated and compared to a chemical oxide layer. The efficient role of thermal oxide or oxynitride layer as a H2O diffusion barrier has been pointed out.

The sealing mechanism of silicon bonding interfaces is reported as a function of annealing temperature. Details of the structural and chemical interface evolution are obtained for hydrophilic silicon/silicon and silicon/silicon dioxide wafer bonding, using x-ray reflectivity and infrared spectroscopy. A two-step mechanism is demonstrated: first a partial sealing of the interface driven by cross-wafer silanol bond condensation and second a water evacuation via oxide formation at the silicon oxide interface.

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