Atomic Layer Deposition of Ru for Replacing Cu-Interconnects

Abstract

The atomic layer deposition (ALD) of Ru using a metal–organic precursor, tricarbonyl­(trimethylenemethane)ruthenium [Ru­(TMM)­(CO)3] and O2 as a reactant is reported. The high vapor pressure, thermal stability, and relatively small ligands of the precursor facilitate efficient ALD. Typical self-limiting growth and an ALD temperature window of 220–260 °C are observed along with significantly high growth per cycle (GPC) (∼1.7 Å) and short incubation cycles (∼6) at 220 °C. Density functional theory calculations indicate that the high growth rate and self-limiting behavior can be attributed to the characteristics of the trimethylenemethane ligand. The as-grown polycrystalline films (average grain size ∼20 nm and negligible impurities) were evident from plan-view transmission electron microscopy. The variation in film resistivity with increasing film thickness and deposition temperature was investigated with and without annealing. Films deposited at 260 °C show low resistivity (∼12.9 μΩ cm), which further decreases (∼9.8 μΩ cm) postannealing at 500 °C. A thin Ru film is successfully deposited with 100% step-coverage on a dual-trench structure having an aspect ratio of ∼6.3 (minimum width: ∼15 nm). The interfacial adhesion energy measured using the four-point bending test exceeds 7 J m–2, regardless of the dielectric material and annealing treatment. The Ru precursor permits enhanced nucleation and GPC at relatively low deposition temperatures to construct high-quality Ru films with significantly low resistivity using simple, plasma-free techniques, and is suitable for the fabrication of emerging Ru films to replace Cu-based interconnects.

Atomic Layer Deposition of Iridium Using a Tricarbonyl Cyclopropenyl Precursor and Oxygen

“…It is often observed that nucleation during ALD is enhanced on catalytic substrates such as Ru. 44,71,72 For either mechanism on Ru, the calculated adsorption energy of the TICP precursor is highly exothermic. The reaction energies of the two reactions on Ru can be summarized as follows A thin Ir film was deposited on a nanoscale 3D structure with a SiO 2 surface to confirm the conformability of our TICP process.…”

“…Considering the surface-dependent growth of Ir by ALD, a Ru thin film was introduced as the seed layer for rapid Ir nucleation. First, the Ru layer was deposited by ALD 44 on a dual-trench structure (top and bottom openings: ∼40 and ∼15 nm, respectively) with an average aspect ratio of ∼6.3. Ru ALD showed no nucleation delay on the SiO 2 substrate, at a deposition temperature of 260 °C.…”

“…In addition, dissociative adsorption of the precursor on metallic Ru involving adsorption of either the tCyp or CO ligands on the Ru surface, separated from Ir, was considered. It is often observed that nucleation during ALD is enhanced on catalytic substrates such as Ru. ,, For either mechanism on Ru, the calculated adsorption energy of the TICP precursor is highly exothermic. The reaction energies of the two reactions on Ru can be summarized as follows …”

“…Deposition was typically conducted on H-terminated Si substrates. Furthermore, the growth behavior on the following surfaces was also investigated: SiO 2 (100 nm), sputtered TiN (thickness: 20 nm on Si), a Ru film grown by ALD using tricarbonyl(trimethylenemethane)ruthenium [Ru(TMM) (CO) 3 ] as a precursor and O 2 as a reactant (thickness: 10 nm on Si), 44 and Al 2 O 3 obtained by ALD using trimethylaluminum [Al(CH 3 ) 3 ] as the precursor and H 2 O as the reactant (thickness: 10 nm/Si). 45 The Ru film also acted as the seed layer for Ir ALD in some experiments.…”

Recent Progress in Physics-Based Modeling of Electromigration in Integrated Circuit Interconnects

“…the current density that induces failure at 10 y. Under such a scenario, interconnects based on Ru and Co are potential replacements with better reliability than Cu because of their lower resistivity and higher EM activation energies [55][56][57][58][59][60]. The barrierless Ru interconnect together with an integration scheme have been identified to be more EM reliable than Cu [61].…”