Topographic measurements of supersmooth dielectric films made with a mechanical profiler and a scanning force...

The roughnesses of five supersmooth dielectric films of Si(3)N(4), TiO(2), HfO(2), Ta(2)O(5), and Al(2)O(3) 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 ∼1-Å-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 Ta(2)O(5) and Al(2)O(3) films was less random than that of the other film materials and the substrates.