TOPOGRAPHIC MEASUREMENTS OF SUPERSMOOTH DIELECTRIC FILMS MADE WITH A MECHANICAL PROFILER AND A SCANNING FORCE MICROSCOPE

The roughnesses of five supersmooth dielectric films of Si3N4, TiO2, HfO2, Ta2O5, and Al2O3 prepared by an ion-beam-sputtering technique were measured with a commercial Talystep mechanical profiler and a sensitive Leica WYKO SPM30 scanning force microscope (SFM) to determine how much roughness the films added to the similar to 1-Angstrom-rms roughness fused-silica substrates on which they were deposited. In all cases the increase in roughness for the three-quarter-wave optical thickness films was a small fraction of an angstrom. SFM measurements showed that the topography of the Ta2O5 and Al2O3 films was less random than that of the other film materials and the substrates.