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.