Quality assessment from supersmooth to rough surfaces by multiple-wavelength light scattering measurement

An apparatus for total integrated backscattering measurement is described that operates in the UV to IR spectral region. Background levels smaller than 0. 1 ppm at 633 nm have been achieved. During the measurement, the sample surface is scanned automatically, yielding one -or two-dimensional scattering diagrams. From the latter, small defects on supersmooth surfaces can be localized. Results are reported of measurements on samples waith different surface qualities such as spersmooth Si-wafers with sub-Angström roughness, CaF2 substrates, thin film optical coatings and rough engineering surfaces. The equipment is involved in standardization project ISO/CD 13696.