Optical Monitoring of Thin-films Using Spectroscopic Ellipsometry

Spectroscopic Ellipsometry (SE) offers a precise technique for measuring thin film properties. Advanced SE instrumentation has been demonstrated as an excellent technique for monitoring the growth of optical films for sputtering applications. We have recently extended this technique for PVD E-gun evaporated films. In this paper we will show how an SE system was integrated into a standard optical coating system with an electron beam source and used for in situ film thickness monitoring of the growth of single layer films. During deposition of the films, the SE provided real time determination of the film thickness and refractive index. Additionally, the SE data was analyzed to study the homogeneity of the films. Finally a model was developed for in situ control of multi-layer stacks and demonstrated for a 3-cavity 17-layer band pass filter.