Metrology of 1–10 nm thick CN_x films: Thickness, density, and surface roughness measurements

Ultrathin nitrogenated carbon (CN_x) films were synthesized using pulsed dc magnetron sputtering. The influence of substrate tilt angle and rotation speed on surface roughness was explored. Atomic force microscopy studies showed that the smoothest films were obtained at substrate tilt of 45° and rotation speed 20–25 rpm, corresponding to 2–3 rotations per deposited atomic layer. The root-mean-square surface roughness under these optimum conditions is ∼0.3 nm when sampled over 20×20 μm² areas, increasing to ∼0.4 nm when sampled over ∼0.05×3 cm² using x-ray reflectivity measurements. In addition, x-ray reflectivity measurements showed that the mass density of these CN_x films is ∼2.0 gm/cc, independent of film thickness from ∼1 to 10 nm, consistent with ion beam analysis. © 2003 American Vacuum Society.