A Meta-Analysis of Non-Copper Nanowire Resistivities

Innovations in back-end-of-line (BEOL) interconnects over the past several decades have been driven primarily by both Moore’s law mandated dimensional scaling of Cu wiring and permittivity scaling of low dielectric constant (i.e. low-<i>k</i>) interlayer dielectrics (ILDs) to mitigate increased resistance-capacitance (RC) delays. However, due to the demand for continued dimensional scaling, the industry now faces an exponential rise in interconnect metal line resistance created by both increased Cu resistivity size effects and limitations in thickness scaling for the Cu diffusion barrier materials needed for yield and reliability considerations. This has created an intense interest for identifying new conductors that exhibit reduced resistivity size effects and / or that require no or reduced thickness diffusion barriers. To support the identification of potential copper replacement conductors, we share a benchmarking Meta-analysis of nanowire resistivities publicly reported in the scientific literature for numerous metals including those currently under active consideration (i.e. Cobalt, Tungsten, Ruthenium, and Molybdenum) as well as up and coming metals (Iridium, Rhodium) and other potentially overlooked metals. We will conclude by examining the supply chain challenges that may ultimately play a role in the selection of future copper replacement conductors and discuss research needed to address these challenges.