Real time control of reactive magnetron-sputter deposited optical filters by in situ spectroscopic ellipsometry

In situ spectroscopic ellipsometry was applied for real-time control of the reactive magnetron sputter process of optical coatings on glass. Single tr ansparent films of SiO2, Si3N4 and SiOxNy with varying composition as well as multilayer optical filters on transparent thick floatglass were fabricat ed. The process control system is based on an optical monitor for the depos ition rate and the film composition in combination with a plasma control se tup. The latter was developed for the short-term stabilization of the mid-f requency magnetron sputter process. The quality of the filters deposited us ing the control system is demonstrated by comparing the calculated reflecti vity and transmission with the experimental ex situ data. The investigation s show that for silicon oxynitride films, the combination of plasma control with ellipsometric control can be used for controlling the stoichiometry o f the growing film. (C) 2000 Elsevier Science B.V. All rights reserved.