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Modeling of very thin aluminum nitride film mechanical properties from nanoindentation measurements

Abstract:

The mechanical property determination of thin films by nanoindentation can be affected by the substrate depending on the indentation testing conditions and the film thickness. In this condition and especially for very thin films, application of models is required for separating the substrate influence of the indentation measurement. In this paper, hardness and elastic modulus of columnar aluminum nitride of 250 nm (thickness) have been determined by nanoindentation. The hardness versus the indenter displacement variation has been studied applying a variety of models to compare their prediction. A specific methodology avoiding the knowledge of the film thickness is proposed. Concerning the elastic modulus determination, different weight functions have been applied without any success since the elastic modulus variation versus the indenter displacement shows typically an 'S' curve whereas the standard models predict a linear variation. Consequently to adequately represent this variation, the models are modified accordingly to Avrami's law. As a main result, the hardness is found to be equal to 10 GPa and the elastic modulus close to 150 GPa.