Inter-ligand reaction-mediated atomic layer deposition of Ru-incorporated MoC_x films for dual-function copper diffusion barriers and seed layers

The continuous downscaling of Cu interconnects requires the development of dual-function materials that serve as both Cu diffusion barriers and seed layers. In this study, ruthenium-incorporated molybdenum carbide (MoC_x(Ru)) thin films were synthesized via inter-ligand reaction-mediated atomic layer deposition (IL-ALD) using bis(ethylbenzene)molybdenum and dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium(II) as Mo and Ru precursors, respectively. The IL-ALD MoC_x(Ru) process exhibited a self-limiting surface reaction with increasing pulse lengths of the Mo and Ru precursors, enabling excellent step coverage (90%) on trench substrates with an aspect ratio of 21:1. The as-deposited MoC_x(Ru) films exhibited nanocrystalline structures with Ru concentrations in the range of 4.4–7.6 at%. After post-deposition annealing at 400–600 °C in a H₂ (4%)/Ar (96%) atmosphere, the films exhibited low resistivity values in the range of 234–532 μΩ·cm. Ultrathin (3–6 nm) MoC_x(Ru) films effectively maintained their Cu diffusion barrier properties up to 500–550 °C, representing an improved barrier performance compared to pure MoC_x films (2–7 nm), where Cu diffusion occurs at 400 °C. Furthermore, the MoC_x(Ru) films demonstrated excellent functionality as Cu seed layers, enabling super-conformal Cu electroplating on trench substrates with minimal void formation. These results highlight IL-ALD MoC_x(Ru) films as promising candidates for next-generation dual-function Cu diffusion barriers and seed layers in advanced semiconductor metallization.