Atomic layer deposition of Ru thin films using a Ru(0) metallorganic precursor and O₂

Ruthenium (Ru) thin filmswere grown on thermally-grown SiO₂ substrate using atomic layer deposition (ALD) by a sequential supply of a zero-valent metallorganic precursor, (ethylbenzyl) (1-ethyl-1,4-cyclohexadienyl) Ru(0) (EBECHRu, C₁₆H₂₂Ru), and molecular oxygen (O ₂) between 140 and 350°C while the typical temperature was 225°C. A self-limiting film growth was confirmed at the deposition temperature of 225°C and the growth rate was∼0.042 nm/cycle on the SiO₂ substrate with a negligible number of incubation cycles (approximately 3 cycles). Plan-view transmission electron microscopy analysis showed that nucleation was started after only 3 ALD cycles and the maximum nuclei density of 1.67 × 1012/cm² was obtained after 7 ALD cycles. A continuous Ru film with a thickness of ∼2.3 nm was formed after 60 ALD cycles. The film resistivity was decreased with increasing deposition temperature, which was closely related to its crystallinity and microstructure, and the minimum resistivity of ∼14 μ-cm was obtained at the deposition temperature of 350°C. The step coverage of the film deposited between 225 and 270°C was approximately 100% over the contact holes (bottom diameter: 0.065 μm) with a high aspect ratio (32:1). Finally, the ALD-Ru film was successfully evaluated in terms of its performance as a seed layer for Cu electroplating and as a bottom electrode for a metal-insulator-metal capacitor using an ALD-TiO₂ single layer or an ALD HfO₂/La ₂O₃/HfO₂ multilayer as a dielectric.