The Characterization of Sputtered Zr-Ge-N Thin Films as Diffusion Barriers Between Copper and Silicon

The main purpose of the present micro-structural analysis by transmission electron microscopy (TEM) and X-ray diffraction (XRD) was to investigate whether amorphous Zr-Ge-N films are a potential candidate as a diffusion barrier for Cu wiring used in Si devices. The Zr-Ge-N films were prepared by a radio frequency (RF) reactive magnetron sputter-deposition technique using N-2 and Ar mixed gas, and the film structure was found to be sensitive to the gas flow ratio of N-2 vs. Ar during sputtering. Polycrystalline Zr-Ge-N films were obtained when the N-2/(Ar+N-2) ratio was smaller than 0.2 and amorphous-like Zr-Ge-N films were obtained when the ratio was larger than 0.3. Diffusion barrier test was performed by annealing the Cu/Zr-Ge-N/Si film stack under Ar atmosphere. The deposited Zr-Ge-N(C) films remained amorphous even after high temperature annealing. The Cu diffusion profile in the film was assessed by the Auger electron spectroscopy (AES). The results indicate that Cu diffusion was minimal in amorphous Zr-Ge-N(C) films even at high annealing temperatures of 800 degrees C.