Finite element modelling of stress-induced fracture in Ti-Si-N films

Nanocomposite coating films have been increasingly used in industrial applications because of their unique mechanical and physical properties. Residual stresses generated during the growth of sputter-deposited thin films due to a strain mismatch between the film and the substrate may lead to significant failure problems. Large residual stresses may generate buckling, delamination and film fracture. Although buckles with cracks in thin films have been experimentally observed, their origins are still not well understood. In this work, finite element simulations in Abaqus/Explicit are employed to study buckling and cracking in Ti-Si-N films on a silicon substrate. Residual stresses in the film are generated using two loading methods: 1) Eigenstrain is applied via a temperature field; 2) An initial stress field is applied. Cracking is modelled using an elastic material model with a brittle fracture criterion that takes into account the tensile strength of the material to initiate damage. It is found that while both loading methods lead to similar buckling patterns and stresses, an initial stress field generates premature film failure and thus the thermal field loading should be used. The numerical model fairly predicted the cracking patterns observed in the experiments. © (2014) Trans Tech Publications, Switzerland.