Ruthenium as a Nanoscale Interconnect Material: Advances in High-Purity Preparation, Process Integration, and Diffusion Barrier Engineering for Future CMOS Nodes

Ruthenium (Ru) has emerged as a critical material for nanoscale interconnects in advanced integrated circuits due to its short electron mean free path (6.59 nm), high melting point (~2334 °C), and superior electromigration resistance. As technology nodes scale toward 2 nm and below, conventional copper interconnects suffer from severe resistivity increases caused by size-dependent electron scattering. This review systematically examines the application progress of Ru in nanoscale interconnect technologies, including buried power rails, backside power distribution networks, and high-aspect-ratio via structures. Unlike copper, Ru eliminates the need for thick diffusion barrier layers such as Ta/TaN, reducing overall resistance and enabling direct integration with low-k dielectrics. Recent breakthroughs in grain boundary engineering, including atomic layer deposition combined with high-temperature annealing, have achieved Ru grain sizes exceeding 100 nm, reducing resistivity to near its theoretical limit (7.6 μΩ· cm). Furthermore, Ru-based diffusion barriers (e.g., RuTiN, Ru–Mo–C, Ru–Mn) and seed layers have demonstrated exceptional performance in suppressing Cu diffusion and enhancing interfacial adhesion. Emerging applications in direct metal etching, airgap integration, self-aligned vias, and two-dimensional material heterojunctions (graphene, MoS 2 ) are also discussed. Finally, this review summarizes current challenges in high-purity Ru preparation, compares chemical and physical synthesis routes, and outlines future directions for metastable phase engineering and low-dimensional Ru structures. The findings position Ru as a transformative material for sustaining nanoelectronic device scaling beyond the 5 nm node.