Size-dependent thermal transport properties of advanced metallic nanowire interconnects

Thermal transport properties of metallic nanowires are crucial to the near-junction heat dissipation of transistors. However, the understanding of the size-dependent thermal conductivity of these advanced interconnect metals is still limited. In this work, we select nine candidate metals and investigate the size effect on thermal transport properties by the mode-level first-principles method combining with the Boltzmann transport equation. Their thermal conductivity, the phonon contribution, and the Lorenz ratio in nanowires with characteristic size from 3 to 30 nm are analyzed. While all these metals have lower bulk thermal conductivity than Cu, we find some of these metals have larger thermal conductivity with characteristic size smaller than 10 nm. We identified that their smaller electron mean free path is the key factor. Moreover, the contribution of phonon thermal conductivity is smaller than 25% to total thermal conductivity. The Lorenz ratio is found to be slightly larger than the Sommerfeld value, mainly due to the phonon contribution. This work can provide important guidance for selecting advanced interconnects in the development of next-generation integrated circuits.