Peel strength in the Cu/Cr/polyimide system

In the microelectronics industry, the adhesion strength of thin metal films to dielectric substrate is often measured by the peel test and the peel strength is directly related to the interfacial fracture resistance. In order to understand the effects of plastic deformation and the interfacial fracture energy on the peel strength, thickness of the metal layer and the pretreatment conditions of polyimide were varied in the Cu/Cr/polyimide system. The work expenditure during the peel test was estimated using the stress strain curves of metal films, X-ray measurements of the plastic strain in the peeled films, and the elastoplastic beam analysis. Results indicate that the peel strength is strongly affected by the film thickness and the pretreatment condition in a synergistic way, and that the measured peel strength is more a measure of the plastic deformation during the peel test than a measure of the true interfacial energy.