Failure of todays’ electronic devices is oftentimes attributed to the detachment of individual, rather confined layers, which themselves carry different functional properties, e.g. semiconducting, wear protection, diffusion barrier, heat sink. Therefore, understanding interfacial fracture processes in the native scale of such miniaturized structures is a necessity if one strives to improve the lifetime of a device.
In the present work, we showcase experimental micromechanical approaches in a plane multi-layered WTi-Cu system, which serves as a representative substitute for classical microelectronic devices with a constituent that exhibits a significant amount of plasticity. To address the fracture behaviour of the interface, in situ microcantilever deflection experiments as well as in situ transmission scanning electron microscopy experiments in tensile (mode I) and shear (mode II) direction were conducted. These experiments were analysed in conjunction with elastic-plastic fracture mechanical concepts, e.g. J-integral or crack tip opening displacement, to account for the high deformability of the Cu phase. Furthermore, one specimen was intentionally exposed to air as opposed to pure vacuum processing during wafer level synthesis to study the influence of interface chemistry of the bi-layer cohesion. The conducted experiments in conjunction with density functional theory simulations and analytical modelling revealed that crack formation along the interface occurs, likely due to a change in local loading mode driven by the accumulation of plasticity in the Cu phase.
In summary, we suggest a combined experimental-computational framework to address elastic-plastic interface properties and their chemical modification on a local scale.