Yttrium carbide thin film as an emerging transition metal carbide Prepared by plasma-enhanced atomic layer deposition for Dual diffusion barrier applications into Cu and Ru metallization

Abstract

Transition metal carbides (TMCs) often possess superior properties to transition metal nitrides (TMNs) in hardness, thermal stability, electrical conductivity, and chemical stability. However, developing an atomic layer deposition (ALD) process for these materials remains in its early stages, especially yttrium carbide (YC_x) thin films, which remained largely unexplored. This study focuses on developing a plasma-enhanced ALD-YC_x process for high-quality, uniform, and conformal thickness control TMCs while highlighting the advanced properties to utilize as advanced diffusion barriers via a novel Y-precursor. The critical experimental process parameters, Y-precursor, and H₂ plasma exposure times are thoroughly optimized to achieve highly conductive (∼415 μΩ·cm), high crystalline PEALD-Y₂C thin films with a growth rate of ∼0.13 nm/cycle at 250 °C within the ALD temperature window (150–350 °C). Advanced aberration-corrected electron microscopies, electron diffractions, and spectroscopic techniques confirmed the formation of a nanocrystalline rhombohedral phase, C-to-Y ratio ∼0.46, 4.63 g/cm³ density, and excellent step coverage (95%) of a trench structure with an aspect ratio of ∼1.5 and a bottom width of ∼265 nm. The post-annealed PEALD-Y₂C films maintained stable thermal and crystallographic properties, exhibiting effective dual diffusion barrier performance for Cu and Ru (∼40 nm) up to 900 °C, emphasizing its importance as interconnects in advanced semiconductor devices.