AVS 47th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS1+MS-WeA

Paper PS1+MS-WeA9
Multiwavelength In-Situ Ellipsometry for Optical Coatings Fabrication: Optimal Control Strategies and Results

Wednesday, October 4, 2000, 4:40 pm, Room 310

Session: Sensors and Control in Plasma Processing
Presenter: A. Hofrichter, Ecole Polytechnique, France
Authors: A. Hofrichter, Ecole Polytechnique, France
D. Kouznetsov, Ecole Polytechnique, France
P. Bulkin, Ecole Polytechnique, France
B. Drevillon, Ecole Polytechnique, France
Correspondent: Click to Email
There is an increasing interest in adopting ellipsometric control for the manufacturing of optical filters. Ellipsometry does not relay on the amplitude of reflected signal, has very high sensitivity to both, thickness and complex refractive index, and can be used directly to probe growing surface, thus it is neither limited to transparent films nor depends on stability of light source. In comparison with such traditional techniques, as quartz crystal monitor and transmission/reflection spectrometer or laser interferometer, it is free of most their problems. However, interpretation of ellipsometric data is much more complicated and usually prevents application of ellipsometers for real-time process control in industrial environment. We present a robust algorithm for feed-back control of the PECVD deposition, based comparison of pre-computed ellipsometric trajectories with real-time data stream. Such approach allows to stop growth of each layer with high accuracy without performing complicated real-time inversion of ellipsometric data. Using our Integrated Distributed Electron Cyclotron Resonance (IDECR) PECVD reactor we performed depositions of multilayer and gradient optical coatings with good agreement with design. The next step will be inclusion of dinamic corrections of gas flows based on real-time determination of refractive index profile.