We detail the thickness-dependent increase of optical scattering in microcrystalline silicon by analysis of specular reflection and angle-resolved scattering measurements with a goniometer. The scattering properties are related to the increase in surface roughness with increasing sample thickness. Analysis of the specular reflection in the ultraviolet spectral range allows a determination of the surface roughness. Manipulation of the surface morphology by mechano-chemical polishing results in lesser optical scattering because polishing reduces the surface roughness and thus surface-related scattering.