TECHNICAL In many applications of multi-component micro-systems, interfaces are subjected to large shear stresses and high homologous temperatures. This enables diffusionally accommodated sliding processes (interfacial creep) to operate at the interface. Furthermore, thin film interconnect structures in micro-systems often carry large electric current densities, which drive electromigration. As interconnect dimensions shrink, interfaces become the primary path for diffusion during electromigration, potentially leading to significant interactions between interfacial diffusive fluxes due to applied stress and electromigration. With the emerging trend towards nano-scale miniaturization of multi-material assemblies in microelectronics, MEMS and functional nano-composites, and the commensurately explosive growth in interfacial area inside these assemblies, interfacial sliding is likely to become increasingly prominent, severely impacting the performance and reliability of the component. Here, a comprehensive experimental and analytical effort is proposed in order to obtain fundamental mechanistic insight into interfacial creep at thin film-substrate interfaces under thermomechanical and electrical loads. The effort will combine creep testing with and without applied electrical current, interfacial characterization, constitutive modeling and experimental/analytical investigations of microelectronic device structures. This study will highlight the interaction between stress and electric current in promoting/inhibiting interfacial sliding. NON-TECHNICAL: The broader impact of the work is related to its technological relevance to the entire micro/nano-systems industry by bringing to light a new phenomenon which may become performance limiting in a wide array of components in the future. Throughout the project, the PI and his group will work closely with the industry to identify/address issues of emerging relevance, and expose students to the industry. In addition to training graduate students and post-docs, the PI and his group will work with high school students through a local enrichment program to expose them to materials research and emerging issues related to micro/nano-systems. Summer internships will also be offered to middle/high school science teachers with the aim of helping them develop lesson modules relevant to the general area of this research.
