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 with different surface qualities such as supersmooth. Si-wafers with sub-Angstrom roughness, CaF2 substrates, thin film optical coatings and rough engineering surfaces. The equipment is involved in standardization project ISO/CD 13696''.