Chemical Vapor Deposition of Cobalt Nitride and its Application as an Adhesion-Enhancing Layer for Advanced Copper Interconnects

摘要

An interlayer of face centered cubic (fcc) C0_4N has demonstrated significant improvements in adhesion between copper and diffusion barrier layers. This fcc phase of Co_4N was prepared by chemical vapor deposition (CVD) using bis(N-tert-butyl-N'-ethyl-propionamidinato)cobalt(II) and a reactant mixture of NH_3 and H_2 at substrate temperatures from 100 to 180°C. The Co/N atomic ratio and the phase of cobalt nitride film can be modified by adjusting the ratio of NH_3 and H_2 in the gas feedstock. The cobalt nitride films prepared by CVD are smooth, highly conformal, and stable against intermixing with copper up to at least 400°C. This fcc cobalt nitride material has very strong adhesion to copper due to the small lattice mismatch (— 1 to 2%) between fcc-C0_4N and fcc Cu. Copper wires should be stabilized against failure by electromigration when fcc cobalt nitride interlayers are placed between the copper and surrounding diffusion barriers.