Plasma-enhanced atomic layer deposition (PEALD) of cobalt thin films for copper direct electroplating

•PEALD Co films for direct Cu plating were deposited using CCTBA precursor.•The H2 plasma treatment increased the nucleation density and wettability of Co films.•The resistivity of Co films decreased with increasing the H2 gas flow rate.

It is challenging to produce reliable Cu wiring on the nanometer scale for scaled-down devices. We studied the use of Co films deposited by plasma-enhanced atomic layer deposition (PEALD) using dicobalt hexacarbonyl tert-butylacetylene (CCTBA) as a precursor for Cu direct plating. Electrical properties of PEALD Co films of sub-20 nm thickness were determined by assessing continuities, morphologies, and impurities. To decrease the resistivity of Co films, a TaNx substrate was pre-treated with H2 plasma and the flow rate of H2 gas during CCTBA feeding and reactant feeding pulses was increased. Co films were deposited on a 3 nm-thick TaNx-covered SiO2 substrate with 24 nm-deep trenches, and Cu direct plating was successfully performed under conventional conditions.