Comparative study of ZrN and Zr-Ge-N thin films as diffusion barriers for Cu metallization on Si

The diffusion barrier properties of Zr-Ge-N and ZrN thin films for Cu metallization on Si have been examined. Both Zr-Ge-N and ZrN thin films deposited at room temperature via reactive magnetron sputtering are amorphous. X-ray diffraction of annealed Cu/nitride/Si structures indicates that a 50 nm thick ZrN film is an effective diffusion barrier for annealing at 600 degrees C for 1 h. In contrast, Zr-Ge-N failed as a diffusion barrier upon annealing at 600 degrees C as evidenced by the appearance of copper silicide diffraction peaks. Cross-section transmission electron microscopy also showed the formation of Cu3Si crystallites at the annealed Zr-Ge-N barrier interfaces. For ZrN barriers annealed at 600 degrees C, the integrity of the nitride/Si interface is preserved and the energy-dispersive spectrometry line scan showed no Cu diffusion through the barrier into Si substrate. The result indicated that ZrN is superior to Zr-Ge-N as a copper diffusion barrier on Si. (C) 2008 American Vacuum Society.