Modeling crack propagation for advanced 4-point bending testing of metal–dielectric thin film stacks

For monitoring and improving mechanical properties of BEoL (back-end of line) interconnect structures in microprocessor technology, it is crucial to analyze their adhesion and crack propagation properties. In the present investigation, a camera assisted 4-point bending beam technique has been used to obtain fast and reliable adhesion measurements including locally resolved crack length information. To interpret the obtained crack propagation data, a finite-element modeling approach has been utilized. The combination of local measurement of the crack energy release rate and modeling enables to evaluate measurement curves for both symmetric and asymmetric crack propagation modes and to describe the crack propagation properties of the involved film stacks not attainable in such detail by conventional 4-point bending technique.

► The force plot in case of asymmetric and symmetric pre-crack looked similar.
► The force plot in the case of single sided crack propagation shows no force plateau.
► The crack propagation curve has a gap when crack advances in different Gc interfaces.