Spectroscopic ellipsometry (SE) and grazing X-ray reflectometry (GXR) analyses on tungsten carbide films for diffusion barrier in copper metallization schemes

Tungsten carbide (WCx, x∼0.5) films, for diffusion barrier applications in copper metallization schemes, were prepared by a pulsed chemical vapor deposition (PCVD). Spectroscopic ellipsometry (SE) and grazing X-ray reflectometry (GXR) were used to characterize WCx films for thickness, surface roughness, and their optical properties. It is found that Drude law with two Lorentz absorption bands could be used to describe the optical dispersion behaviors of WCx films. Structural and chemical characterization of the films was performed with Auger electron spectroscopy (AES), X-ray diffraction spectroscopy (XRD), and atomic force microscopy (AFM). Surface roughness obtained from GXR and SE is consistent with AFM measurements