Abstract

Angle resolved scatter measurements were performed on fused silica superpolished substrates. The total scatter from these substrates is caused by surface, near surface, and bulk scatter. The total scatter from the substrate was measured at 0.633 μm with the Phillips Laboratory scatterometer. Bulk scatter was measured by a method independent of the surface and near surface scatter. The measured bulk scatter was subtracted from the total scatter. The angular profile of the residual scatter compares favorably to the optical factor in the Rayleigh-Rice interface scatter theory. The optical factor, a term in the theory dependent on index of refraction and source and detector polarization, was then removed from the residual total scatter. The remaining scatter was integrated to determine the total integrated scatter for incident beam angles of 25°, 40°, 60°, and 80°. The resulting integrated values were corrected for the variation in transmitted power according to the Fresnel equations and were plotted versus the incident angle. The plotted curves demonstrate that the method developed to measure the scatter combined with analysis using Rayleigh-Rice theory allow the strength of near surface scatter to be estimated.

© 1992 Optical Society of America