Micro Tensile Tests on Aluminium Thin films: Tensile Device and In-Situ Observations
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1139-GG04-04
Micro Tensile Tests on Aluminium Thin films: Tensile Device and In-Situ Observations M. Ignat1, S.Lay1, F. Roussel-Dherbey1, C. Seguineau1,3 , C. Malhaire2, Xavier Lafontan3, J.M. Desmarres4,S.Brida5 1
ENSEEG INPG, SIMAP UMR 5266, Université Joseph Fourier, F-38402, France. Université de Lyon, INSA-Lyon, INL, CNRS UMR 5270, Villeurbanne, F-69621France. 3 Nova MEMS, 10 av. de l’Europe, Ramonville, F-31520, France. 4 CNES, DCT/AQ/LE, bpi 1414, 18 Avenue Edouard Belin, Toulouse F-31401, France. 5 AUXITROL S.A. , Esterline Sensors Group, Bourges, F-18941, France.
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ABSTRACT The results of micromechanical tensile experiments performed on thin aluminum samples are presented and discussed. The micro tensile test system and the design of the samples, based on finite element modeling (FEM), and their production by micromachining are briefly described. Some examples of the stress strain curves are presented. The Young’s modulus and critical parameters (flow and rupture stress and strains) are reported. The micro structural changes induced by the tensile experiment were observed during and after the testing by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). INTRODUCTION To understand the reliability issues that limit MEMS design and application, it is essential to have adequate understanding of the mechanical stability of the materials to be used; cconsequently, determining the mechanical properties for MEMS materials continues to be a fundamental research objective. Material parameters, such as Young’s modulus and the flow and failure stress, which depend both on microstructure and applied loading modes, need to be measured; see, for example, references[1-3] . In contrast with the case of bulk materials, for thin films a lack of information on their mechanical properties will be a continuing problem. Since their mechanical properties are strongly dependent on the microstructure and, as the microstructure will change with the deposition process, for the same thin material, different processes will produce different microstructures, and different mechanical behavior. Generally, micro tensile experiments on thin self standing samples, differ either in the way of attaching the samples to the tensile device (detached or semidetached with respect to the substrate), or the sample geometry, which often determines how the displacement and force are applied and measured during a tensile experiment [1-3]. The new equipment is based on a device previously developed to perform in-situ tests in a SEM, on film on substrate systems (for details of that previous device and some results obtained with it see references [4-6]).
Even though with that device it was not possible to obtain significant results on self standing thin films, the original concept: to induce a symmetrical displacement of the grips, thus avoiding any drift in image observation, was kept for the micro tensile system described here. The preparation of submicron thickness, self standing, tensile-test specimens of metallic or d
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