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 SiOx (N-SiOx) 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-SiOx and T-SiO2 exhibit pronounced nucleation delay. N-SiOx 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-SiOx). 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.
Ha et al. (Wed,) studied this question.