Impurity-controlled Ru thin films via hollow cathode plasma-enhanced atomic layer deposition with low resistivity and high conformality

This study explores the deposition of ruthenium (Ru) thin films using a hollow cathode plasma-enhanced atomic layer deposition (HCP-ALD) process at 250 °C with oxygen as the reactant. The hollow cathode configuration enables the generation of reactive oxygen species under low-power plasma conditions while minimizing ion-induced damage. This promotes ligand removal and improves surface reactivity, leading to high-purity Ru films with enhanced properties. Under the optimized condition, the film exhibits a growth per cycle of 0.76 Å/cycle, a density of 11.8 g/cm 3 , and a low oxygen impurity concentration. Post-deposition annealing in a reducing atmosphere enhances crystallinity and removes residual oxygen, while the film maintains a low surface roughness of 0.96 nm due to its uniform growth. Resistivity is reduced to 11.9 μΩ·cm at a thickness of 20 nm, attributed to minimized electron scattering at grain boundaries, surfaces, and impurities. Step coverage of 88% is achieved in trench structures with an aspect ratio of 12:1, confirming excellent conformality. These findings demonstrate that the HCP-ALD technique enables high-purity and conformal Ru film growth, making it a promising candidate for future interconnect and electrode applications in advanced semiconductor devices.