Directional and Topological Conductors for Scaled Interconnects

Copper (Cu) interconnects, widely used in modern integrated circuits (ICs), are increasingly the bottleneck for scaling driven by Moore’s Law. The rising resistivity of Cu falls short of industry requirements, largely due to the electron surface scattering inherent to Cu’s isotropic electronic structure. In this context, my study focuses on three promising alternative interconnect materials, which are expected to outperform effective Cu at smaller dimensions. First, we investigate the directional conductor delafossite oxide PtCoO2 which features a low bulk resistivity and a distinctive anisotropic structure that mitigates electron surface scattering. PtCoO2 thin films are synthesized by MBE, followed by post-deposition annealing, with their high quality confirmed by various characterization techniques. Importantly, the thickness-dependent resistivity curve shows that PtCoO2 significantly outperforms effective Cu and Ru. Furthermore, PtCoO2 exhibits excellent stability under oxygen exposure and in contact with other materials, affirming its compatibility with existing IC manufacturing processes. These findings position PtCoO2 as a promising candidate for future interconnect technologies. Next, we explore the topological conductor CoSi, which possesses non-trivial surface states. Initial investigations on CoSi thin films were unable to probe the topological properties due to textured polycrystallinity. To overcome this limitation, single-crystal CoSi nanobelts were grown on HOPG using MBE. The well-defined morphology and single crystalline nature of the CoSi nanobelts are confirmed by Raman spectroscopy, SEM, and TEM. Our results show that the resistivity of CoSi nanobelts decreases with reduced cross-sectional area, indicating topologically protected surface transport and positioning topological conductors as promising candidates for scaled interconnects. Finally, encouraged by CoSi results, we explore PdGa, a topological conductor with a significantly lower bulk resistivity. Single-crystal PdGa nanobelts were synthesized on the HOPG substrate. Intriguingly, TEM diffraction patterns indicate a previously unreported crystal structure in these nanobelts. This novel phase suggests new avenues for structural and electronic exploration in PdGa.<p></p>