Scalability of RuTiN barriers deposited by plasma-enhanced atomic layer deposition for advanced interconnects

Abstract

A tri-layered in situ grown RuTiN barrier system for advanced interconnects was developed using plasma-enhanced atomic layer deposition (PE-ALD) from tetrakis(dimethylamino)titanium, (pyrrolyl-methylcyclopentadienyl)ruthenium and N2/H2 plasma. The system consists of an ultrathin TiN nucleation layer to enable Ru growth on Si oxide substrates, a bulk RuTiN layer, and a top Ru film to ensure compatibility with Cu and electrochemical Cu deposition techniques. It is shown that the nucleation layer does not need to be continuous and that 0.6–0.7nm is sufficient to enable Ru nucleation on oxides. Layer closure studies of a Ru cap grown on RuTiN films indicate that the minimal thickness to have a closed Ru layer at the top surface is around 1.0nm. 3nm RuTiN films show good oxidation resistance and Cu barrier properties for interconnect applications when compared to the well-known TaN barrier system. Furthermore, conformal deposition in narrow lines has been obtained. As such, we demonstrate that using the flexibility of the PE-ALD process, composition controllability of the bulk and interfaces can be achieved for sub 3nm thin RuTiN barriers. The interface composition can be optimized for compatibility with bottom and top layers, which makes the system a viable candidate for future interconnect technologies.