Application of composite hardness models to copper thin film hardness measurement

The hardness of copper thin films with thicknesses ranging from 25 to 500 nm on oxidised silicon substrates is investigated. The Oliver and Pharr method is used to analyse the load–displacement curves obtained from nanoindentation. Five composite hardness models (Jönnson and Hogmark, Burnett and Rickerby, Chicot and Lesage, Korsunksy, and Puchi-Cabrera) are applied to the experimental data in order to distinguish film and substrate hardnesses. Both the Korsunksy and Puchi-Cabrera models give very good fits to the data and predict film and substrate hardnesses that would be expected for this film/substrate system. However, the goodness of fit for both these models is dependent on a wide range of normalised depths being represented in the experimental data.