Single-crystalline CoSi semimetals with high conductivity and reliability

As the size of state-of-the-art copper interconnects shrinks to the nanoscale, carrier scattering greatly increases their resistance, causing signal delay and reliability issues. Alternative conductors are therefore needed to sustain interconnect scaling beyond conventional charge-transport mechanisms. Here we demonstrate CoSi semimetal for highly scalable, conductive and reliable interconnects. As the CoSi thickness decreases from 1 µm to ∼20 nm, its resistivity decreases from 7.0 to 0.72 μΩ·cm due to the highly conductive surface path. The room-temperature resistivity of 20-nm-thick CoSi is one-tenth that of copper at the same thickness. The high cohesive energy (5.4 eV) and migration barrier (3.7 eV) of CoSi confer excellent reliability at current densities of up to 10⁸ A cm^-2 and temperatures up to 450 °C. Radiofrequency measurements demonstrate CoSi interconnect operation at frequencies up to 40 GHz. We further integrate a CoSi interconnect with a 16-nm-node silicon ring oscillator, which operates at the same frequency as its metal-interconnected counterpart.