Influence of the preferred orientation and thickness of zirconium nitride films on the diffusion property in copper

Abstract

Zirconium nitride (ZrN) films of different preferred orientations are grown on Si (100) substrates at various substrate temperatures during deposition in a dc magnetron sputtering system. The thermal stability of the as-deposited ZrN films are shown to be stable with Si up to 900 °C annealing for 30 min. The structural characterization of the thin films is carried out by x-ray diffraction and the electrical resistivity is measured by four-point probe. The decrease of the resistivity in the as-deposited films upon annealing is ascribed to the release of the lattice strain. Subsequently, copper is deposited on top of the ZrN films and the interdiffusion of each species upon annealing is studied by Auger electron spectroscopy as a function of ZrN preferred orientation and thickness. The diffusion coefficient and activation energy of Cu in the ZrN barrier are derived. The results indicate that the thicker (111) oriented crystalline ZrN films with larger grain sizes provide a higher activation energy against Cu diffusion and can act as an excellent diffusion barrier for Cu up to 800 °C. The detailed mechanisms accounted for the better performance are discussed in terms of a proposed grain boundary model.