Predicting the Morphology of Cobalt, Copper, and Ruthenium on TaN for Interconnect Metal Deposition

Downscaling of metal interconnects has become a bottleneck in the back-end-of-line processing of CMOS devices. The conductivity of the commonly used Cu metal drastically reduces at nanoscale, limiting its use as the devices shrink, as the metal starts forming non-conductive islands. This has led to the requirement for new interconnect metals such as Co and Ru, as they have a much higher tendency to form conductive films at nanoscale. Understanding how the morphology depends on the metals’ atomistic properties is necessary to continue the rapid development of interconnects. In this study we have used first principles density functional theory calculations to investigate how the morphology of Cu, Co, and Ru differs on TaN substrates. We investigate the binding of both singe metal atoms and different configurations of four atom clusters to obtain the metals’ binding energy to the surface and their clustering energy. The morphology of the metals was then investigated by finite temperature ab initio molecular dynamic simulations of larger metal structures that can display 2D and 3D morphologies. Comparing the binding energies with the obtained morphology allows us to conclude the effect the energies have on the morphology. These insights helps in the development of morphology predictors allowing a quick method for finding new interconnect materials.