Characterization of sputtered nano-crystalline zirconiur carbide as a diffusion barrier for Cu metallization

Zirconium carbide (ZrC) films were grown on Si (100) substrates using magnetron sputtering where the growth temperature (T_ss) was varied from 25°C to 290°C. The microstructure and resistivity of the as-deposited ZrC films were examined. The results reveal that nano-crystalline ZrC films with grain size less than 5 nm were fabricated only at 29°C, which can be explained by a repeated nucleation mechanism. For thermal stability characterization, the stacked structure of Cu/ZrC/Si was subsequently subject to thermal treatments at temperatures from 300°C to 900°C for 30 min in a vacuum tube. The stacked samples were shown to be thermally stable up to about 800°C from Auger electron spectroscopy (AES) and x-ray diffraction (XRD). The diffusion coefficient and activation energy of Cu and Si in the ZrC barrier were also derived. It indicated that Si has a lower activation energy than Cu resulting in faster diffusion. The device completely fails at 900°C, and the mechanism is discussed in this paper.