Abstract
Copper is the current interconnect metal of choice in integrated circuits. As interconnect dimensions decrease, the resistivity of copper increases dramatically because of electron scattering from surfaces, impurities, and grain boundaries (GBs), and threatens to stymie continued device scaling. Lacking direct measurements of individual scattering sources, understanding of the relative importance of these scattering mechanisms has largely been relied on semi-empirical modeling. Here we present the first attempt to measure and calculate individual GB resistances in copper nanowires with a one-to-one correspondence to the GB structure. Four-probe scanning tunneling microscope measurements show discrete resistance jumps across high-angle random GBs and negligibly small resistances across coincidence boundaries. The latter is substantiated by first-principles calculations, while the former is consistent with the prediction of an intrinsic high resistance for random boundaries from a free-electron boundary scattering model. Such a big difference between these GBs provides vital information for nanoscale interconnect technology.
