Institute of Fundamental Technological Research

In this work, we focused on investigations of mechanical properties of SiNx and diamond-like carbon thin films deposited by plasma-enhanced chemical vapour deposition method for application in optical devices or solar cells. Mechanical properties of thin films deposited on clean and oxidized silicon substrates were determined by nanoindentation. The main difficulty with the characterization of thin films using nanoindentation method is related to the influence of the substrate on the measured properties of thin layers. We proposed a method to determine the mechanical properties (hardness and Young's modulus) of thin films in single-layer/substrate or double-layer/substrate system through combining the finite element method, nanoindentation experiments and numerical simulations. In this study, a three-dimensional numerical model of nanoindentation tests performed with Vickers diamond indenter was examined to determine the stress distributions during measurement with various maximum loads. The hardness and Young's modulus of the examined layers were determined using two types of procedures, depending on the von Mises equivalent stress distribution obtained at the maximum load. If the size of an elastically deformed region was sufficiently small compared with the thickness of the measured layers, we applied a standard method of measuring at the depth equal to 10% of the layer thickness; otherwise, an approximation method was used to reduce the substrate influence.

silicon nitride, DLC, PECVD, mechanical properties, nanoindentation, FEM