Property improvement of copper films with zirconium additive for ULSI interconnects

Thermal stability of Cu-Zr/Zr-Si/Si connect system was evaluated by a standard four-point probe (FPP) method, X-ray diffraction (XRD) and Auger electron spectroscopy (AES) analyses. And the Cu/Zr-Si/Si connect system was used as control experiment. XRD spectra for the Cu-Zr/Zr-Si/Si and Cu/Zr-Si/Si stacked films after annealing showed that the Cu-Zr/Zr-Si/Si specimen was stable up to 650 °C. However, the peaks of Cu silicide (Cu₃Si) appeared for Cu/Zr-Si/Si specimen after annealing at 650 °C. The formation of high resistivity Cu₃Si corresponding to the drastic increase in sheet resistance of copper film. The results observed by AES were consistent with those obtained from XRD measurements and demonstrated that Cu-Zr/Zr-Si/Si system had more thermal stability than that of the Cu/Zr-Si/Si system. The thermal stability of Cu-Zr/Zr-Si/Si specimen was obviously improved when Zr was introduced into Cu film.