Interfacial creep in multi-component material systems

Large shear stresses may develop at interfaces between dissimilar materials during thermo-mechanical excursions when there is a significant difference in the coefficient of thermal expansion between them. Most typically, these shear stresses are confined to the extremities of one of the components, such as fiber ends in a composite or the edges of a thin film on a substrate. However when the dimensions of the components are small, these shear stresses may prevail over a large area fraction of the total interface. Under appropriate thermal-mechanical conditions, the interface may slide via diffusional processes, thereby accommodating relative dimensional changes between the phases. This article presents experiments to determine the kinetics and mechanism of interfacial creep, along with evidence of this phenomenon in metal-matrix composites, thin films on substrates, and interconnect structures in microelectronic devices.