SPINNING DEPOSITION OF SILICA AND SILICA-TITANIA OPTICAL COATINGS - AROUND-ROBIN TEST

A round robin test has been performed on sol-gel processing for the de position of silica and silica-titania films on silicon substrates by s pin-coating. Three solution preparation processes for silica coatings and three for silica-titania coatings were used to prepare samples at each of the participating laboratories. The films have been characteri zed mainly by thickness (profilometry and ellipsometry measurements), refractive index, porosity, and optical scattering. Different processe s gave different thicknesses. Thickness differences were found in film s prepared by the same process and by the same deposition parameters, but in different laboratories, when heat-treated at 500 degrees C. Var iations were reduced in samples annealed at 1000 degrees C. Refractive index and porosity measurements suggest that variations were due to s tructural differences, particularly porosity. Furthermore, films heat- treated at 500 degrees C were not completely stabilized, and showed in dex and porosity variations after six months.