Coupled Roles of Surface Chemistry and Hydrogen-Assisted Cycling in Ruthenium Atomic Layer Deposition on Silicon...

Ruthenium (Ru) is a promising interconnect material for advanced semiconductor technologies due to its favorable scaling characteristics, including a short electron mean free path and strong electromigration resistance. In semiconductor integration, silicon oxide-based dielectrics serve as dominant insulating materials and constitute ubiquitous interfaces for metallization; however, their formation-dependent surface chemistry and its impact on Ru growth remain insufficiently explored. Here, we investigate Ru ALD on native oxide SiO _x (N-SiO _x ) and thermally grown SiO₂ (T-SiO₂) as model substrates using bis-(ethylcyclopentadienyl)-ruthenium-(II) [Ru-(EtCp)₂] under two distinct reactant-sequence environments: AB-type (Ru-(EtCp)₂/O₂) and hydrogen-assisted ABC-type (Ru-(EtCp)₂/O₂/H₂). Under the AB-type process, both N-SiO _x and T-SiO₂ exhibit pronounced nucleation delay. N-SiO _x shows earlier nucleation and higher nucleation density than T-SiO₂, plausibly attributed to differences in surface hydroxyl populations. Similar temperature-dependent phase evolution is observed on both substrates, with mixed Ru and RuO₂ phases at 250 °C and predominantly metallic Ru at 300 °C accompanied by increased morphological roughening. In contrast, incorporating an H₂ subpulse (ABC-type) mitigates nucleation delay, particularly on hydroxyl-deficient T-SiO₂, thereby reducing the substrate-dependent disparity observed under AB cycling. Moreover, RuO₂ formation is suppressed even at 250 °C on both substrates, shifting growth toward more metallic Ru with reduced resistivity (∼20 μΩ·cm at ∼ 20 nm on N-SiO _x ). These trends suggest that H₂ influences the surface reaction pathway, contributing to enhanced metallic stabilization and altered early stage growth kinetics. Overall, this work clarifies the coupled roles of substrate chemistry and reactant-sequence design in governing Ru nucleation and early stage film evolution, providing insight relevant to next-generation interconnect integration and future area-selective deposition strategies.