Bulk scattering properties of synthetic fused silica at 193 nm.

The bulk scattering of synthetic fused silica for 193 nm lithography was investigated using an instrument for high-sensitive total and angle resolved scattering measurements at 193 nm. Bulk scattering coefficients alpha between 0.6x10(-3) and 1.7x10(-3) cm(-1) (base e) depending on the hydroxyl (OH) content and fictive temperature of the samples were measured using a total scattering (TS) technique. The results are interpreted with regard to a model which relates scattering in fused silica to structural disorder in the material. From angle resolved scatter (ARS) measurements at 193 nm, a Rayleigh type scattering distribution was found. Using TS and ARS at 633 nm, 532 nm, and 325 nm in addition to the results at 193 nm, wavelength scaling ~n(8)/ lambda(4) as predicted by theory is obtained. Thus, the model is demonstrated to hold from the visible spectral range down to the deep ultraviolet.