Dynamic delamination of patterned thin films: a numerical study

We present an analytical investigation of a test protocol recently developed to extract the fracture toughness of thin films used in microelectronics and other engineering applications. The testing method involves the dynamic delamination of patterned thin films initiated by a laser-induced pressure pulse applied on the backside of the substrate. The kinetic energy imparted by the pulse to a weakly bonded (pre-cracked) region of the film is converted into fracture energy as the thin film delaminates in a controlled fashion over multiple milimeters. To support these experiments and extract the interface fracture toughness values, we develop a numerical scheme based on the combination of a nonlinear beam model used to capture the elastodynamic response of the thin film and a cohesive failure model to simulate the spontaneous propagation of the delamination front. The accuracy of the beam model is assessed through a comparison with the results of a more complex 2D hybrid spectral/finite element scheme. Numerical results are compared with experimental measurements of the delamination length and the outcome of a parametric study of some of the key geometrical and loading quantities defining the delamination event is presented.