Evaluating the Potential of Weyl Semimetals as Future Interconnect Metals

Abstract

A major hurdle in scaling down the size of integrated circuits is the increased resistivity of metallic Back-End-Of-Line (BEOL) interconnects at smaller dimensions. Enhanced surface and grain boundary scattering in the narrow limit leads to dramatic increase in the resistivity of the metal nanowires. Research in the last decade has focused on the search for highly conductive elemental metals like Co, Ru, Ir and Rh which could potentially replace the ubiquitously used Cu. Here, we explore the use of Weyl semimetals as next-generation interconnect materials. Using Density Functional Theory (DFT) coupled with Non-Equilibrium Green’s function (NEGF) calculations, we predict the electron transport characteristics of thin films of a typical Weyl semimetal, namely, NbAs. Studies have shown that in the case of Cu, the resistance area (RA) product remains constant for pristine films and increases for films with defects with decreasing thickness. However, our calculations show that the RA product decreases with film thickness for perfect NbAs films. This is attributed to the disproportionately large number of surface conduction states which dominate the ballistic conductance by up to 50%. Next, we investigate the effect of various types of defects on the electron transport and RA product scaling in different film thickness of NbAs. Our study also investigates the impact of spin-orbit coupling on conductance scaling in the NbAs-family of Weyl semimetals. The results presented here underscore the promise of topological semimetals like NbAs as a future BEOL interconnect metal.