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.