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 O-2 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 degrees C are observed along with significantly high growth per cycle (GPC) (similar to 1.7 A) and short incubation cycles (similar to 6) at 220 degrees 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 similar to 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 degrees C show low resistivity (similar to 12.9 mu Omega cm), which further decreases (similar to 9.8 mu Omega cm) postannealing at 500 degrees C. A thin Ru film is successfully deposited with 100% step-coverage on a dual-trench structure having an aspect ratio of similar to 6.3 (minimum width: similar to 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.