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Accurate measurement of the mechanical properties of ultra-thin films with thicknesses typically below 100 nm is a challenging issue with an interest in many fields involving coating technologies, microelectronics, and MEMS. A bilayer curvature based method is developed for the simultaneous determination of the elastic mismatch strain and Young's modulus of ultra-thin films. The idea is to deposit the film or coating on very thin cantilevers in order to amplify the curvature compared to a traditional "Stoney" wafer curvature test, hence the terminology "micro-Stoney." The data reduction is based on the comparison of the curvatures obtained for different supporting layer thicknesses. The elastic mismatch strain and Young's modulus are obtained from curvature measurements of cantilevers before and after the film deposition. The data reduction scheme relies on both analytical and finite element calculations, depending on the magnitude of the curvature. The experimental validation has been performed on ultra-thin low pressure chemical vapor deposited silicon nitride films with thickness ranging between 54 and 133 nm deposited on silicon cantilevers. The technique is sensitive to the cantilever geometry, in particular, to the thickness ratio and width/thickness ratio. Therefore, the precision in the determination of the latter quantities determines the accuracy on the extracted elastic mismatch strain and elastic modulus. The method can be potentially applied to films as thin as a few nanometers.

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The determination of the mechanical properties of porous amorphous Al 2 O 3 thin films is essential to address reliability issues in wear-resistant, optical and electronic coating applications. Testing the mechanical properties of Al 2 O 3 films thinner than 200 nm is challenging, and the link between the mechanical behavior and the microstructure of such films is largely unknown. Herein, we report on the elastic and viscoplastic mechanical properties of amorphous Al 2 O 3 thin films synthesized by reactive magnetron sputtering using a combination of internal stress, nanoindentation, and on-chip uniaxial tensile testing characterization, together with mechanical homogenization models to separate the effect of porosity from intrinsic variations of the response of the sound material. The porosity is made of voids with 2 to 30 nm diameter. The Young's modulus and hardness of the films decrease by a factor of two when the deposition pressure increases from 1.2 to 8 mTorr. The contribution of porosity was found to be small, and a change in the atomic structure of the amorphous Al 2 O 3 matrix is hypothesized to be the main contributing factor. The activation volume associated to the viscoplastic mechanism is around 100 . Differences in the atomic structure of the films could not be revealed by electron diffraction, pointing to a minute effect of atomic arrangement on the elastic properties.