Improvements in thermal stability of cobalt-silicide films by adding nickel

We studied the diffusion of cobalt atoms into silicon substrates by using an X-ray diffraction experiment and molecular dynamics (MD) simulations to prevent open-circuit failures induced by the agglomeration of cobalt-silicide (CoSi₂) film in semiconductor devices. The experimental results revealed that the agglomeration of cobalt-silicide films was caused by the diffusion of Co-atoms from CoSi₂ films with a (111) texture into Si (001) substrates. The activation energy of Co-atom diffusion measured with sheet resistance (3.6eV) agreed well with that obtained from the MD simulations (3.7eV). We developed a CoSi₂ film by adding nickel (Ni), because the MD simulation results indicated that the addition of Ni effectively reduced diffusion of Co-atoms. Its effectiveness was confirmed by measuring the sheet resistance. The agglomeration rate of CoSi₂ film with Ni added was one digit smaller than that of CoSi₂ film without it.