I have been using a spectroscopic ellipsometer (J.A. Woollam M-44 WVASE) to monitor the thin films in situ. The ellipsometer measures psi and delta, which are the conventional ellipsometric angles. Various optical models, such as the Cauchy model, Bruggeman's effective medium approximation (BEMA) and standard optical data (for example, Si02) can be used to fit the experimentally obtained psi and delta data. The thickness of the film, and also the optical constants, n and k, can then be determined.
SiO2 films are generally quite easy to model. However, the a-Si films have been quite difficult to model and more work needs to be done on correlating other analyses (such as RBS and SIMS) with the results from the ellipsometer.
I have also measured ex situ the composition and thickness of SiO2 films deposited in HARE with the ellipsometer. The Si02 films were deposited by reacting evaporated Si (using an electron beam) with oxygen in the HARE device with a plasma. The films that I've looked at so far were prepared by Dr Antoine Durandet and Dr Craig Davis.
Sarah Hatch
SP3 Group
Plasma Research Laboratory
Research School of Physical Sciences and Engineering
The Australian National University
Canberra ACT 0200
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