In situ monitoring of optical coatings on architectural glass and comparison of the accuracy of the layer thickness attainable with ellipsometry and photometry

Spectroscopic ellipsometry and spectral photometry have been applied for th e deposition of optical coatings on architectural glass. For the purpose of achieving a high competitiveness of manufacturing plants, high deposition rates as well as low scrap quantities are important. The first can be obtai ned by using the mid-frequency (MF) sputtering technique developed at the b eginning of the 1990s for the deposition of highly isolating materials. The latter can be improved by using an effective plasma control and a monitor of the optical film properties. In order to obtain constant layer propertie s, not only the MF but also the direct-current (DC) sputter process has to be stabilized within a relatively narrow process window, which necessitates a suitable plasma control as well as optical monitoring. Spectroscopic ell ipsometry as well as spectral photometry are used for monitoring the optica l properties of SnO2-based low-e-coatings on architectural glass. It is sho wn that spectroscopic ellipsometry is distinctly more sensitive for monitor ing the thickness of low-e coatings than spectral photometry. (C) 2001 Else vier Science B.V, All rights reserved.