Characterisation and modelling of the nanoindentation experiment in Au layers

The nanoindentation experiment is an established technique for the determination of hardness and Young´s modulus of thin films. This standard data set is not sufficient to be used as input to finite element simulations , because elastic-plastic material data is being required for analysis of reliability of metal layers. Therefore stress-strain curves are being determined by fitting the force displacement curves of the experiment with a finite-element model. Additionally this approach enables a solution for the so called substrate effect, because the stiffness of the substrate can be considered in the fitting model. This known approach is being applied and tested on thin (< 500 nm) gold layers deposited on silicon. It is shown that even for indents that exceed 10% of the film thickness a good sensitivity for Young´s modulus can be reached, but for the plastic data the results are not unique and a range of plastic properties can be fitted. It is shown, that this problem of the method can be solved by correlation of the indent profiles.