Self‐Formation of a Ru/ZnO Multifunctional Bilayer for the Next‐Generation Interconnect Technology via Area‐Selective Atomic Layer Deposition

Abstract

AbstractThis study suggests a Ru/ZnO bilayer grown using area‐selective atomic layer deposition (AS‐ALD) as a multifunctional layer for advanced Cu metallization. As a diffusion barrier and glue layer, ZnO is selectively grown on SiO2, excluding Cu, where Ru, as a liner and seed layer, is grown on both surfaces. Dodecanethiol (DDT) is used as an inhibitor for the AS‐ALD of ZnO using diethylzinc and H2O at 120 °C. H2 plasma treatment removes the DDT adsorbed on Cu, forming inhibitor‐free surfaces. The ALD‐Ru film is then successfully deposited at 220 °C using tricarbonyl(trimethylenemethane)ruthenium and O2. The Cu/bilayer/Si structural and electrical properties are investigated to determine the diffusion barrier performance of the bilayer film. Copper silicide is not formed without the conductivity degradation of the Cu/bilayer/Si structure, even after annealing at 700 °C. The effect of ZnO on the Ru/SiO2 structure interfacial adhesion energy is investigated using a double‐cantilever‐beam test and is found to increase with ZnO between Ru and SiO2. Consequently, the Ru/ZnO bilayer can be a multifunctional layer for advanced Cu interconnects. Additionally, the formation of a bottomless barrier by eliminating ZnO on the via bottom, or Cu, is expected to decrease the via resistance for the ever‐shrinking Cu lines.