Improvements in Thermal Stability of Cobalt-Silicide Films by Adding Nickel
Hiromi SHIMAZU, Tomio IWASAKI, Hiroyuki OHTA and Hideo MIURA
Abstract: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. Key Words:Thin film, Thermal stability, Agglomeration, Sheet resistance, Cobalt silicide