As the transistor node technology is moving to 22 nm node and beyond, precise measurement of ultra-thin films is required. The HfO2 gate dielectric films are in the sub 20 A range at this technology node. X-Ray Reflectivity (XRR) is the only non-contact, non-destructive standardless technique to measure thickness, density and roughness of ultra thin amorphous, polycrystalline and single crystal metal films at this thickness range.
One of the main process challenges while depositing the Hf based gate oxides is the uniformity of the ultra thin films. The industry standard is < 3% relative standard deviation. Hence, a fast accurate mapping of this film is very important for the process development.
To control the thickness and density of the ultra thin HfO2 films, XRR is the most effective metrology technique. Moreover, the XRR metrology tools must be suited for FAB environment with complete automation, high angular resolution, low background of the signal and powerful fitting software.
