Interfacial relationships in microelectronic devices

The continued shrink of interconnect structures is requiring new materials to be introduced into back-end of the line (BEOL) devices at an increasing rate. These new materials must provide a performance benefit from the previous generation with the recent focus on reducing the effective dielectric constant of the integrated structures. This reduction may occur not only by changing the intralevel dielectric but also by changing the capping layer/diffusion barrier on the chemical-mechanically polished (CMP'd) Cu surface. However, changing this material may alter the reliability of the device structure due to a change in the Cu/cap interface bonding. Another consequence of the decrease in minimum feature size in interconnects is that commonly practiced techniques, such as sputtered liner and Cu seed, may not be extendable to future generations. Accordingly, the focus of this paper is on identifying basic relationships between interfacial chemistry and interfacial adhesion and illustrating how those relationships can be used to address some of the issues that may pose problems in future technologies.