Amorphous C-Ni superlattice films designed as normal-incidence reflector for 5 nm have been grown on quartz substrate by magnetron sputter deposition. A new digital signal processor-based atomic force microscope (AFM) system has been involved in investigating the surface topography of the final surface of the multilayer structure as well as the substrate. In the first step, roughness measurements involving AFM-tips with different radius curvature indicate the C-Ni multilayer surface profile as being in the nanometer and sub-nanometer range, representing a high quality ended surface of the reflectors. In the second step, a study of the roughness distribution using power spectral density functions (PSD) calculated from AFM measurements was performed. The analysis of the amplitudes of the PSD spectra for the multilayer and the substrate surface provided the evidence of the optimized deposition parameters. The shape of the PSD curves for multilayer and substrate reveals fractal profiles with the same distribution of the roughness for both of them, attesting the influence of the substrate on the quality of the reflectors.