Unclassified Report: Flow of a Gravity Driven Thin Liquid Film over Topographies

The coating of thin films on substrates remains an important activity for Philips’ products, like displays, electronic devices and storage media. A characteristic of these products is that they display topographies, or chemical heterogeneities. We are therefore interested in understanding the formation of coating layers from liquid phase on such substrates. This work concentrates on geometric topographies. A gravity driven set-up simulates this spin coating phenomenon. Some 1D experiments have already been performed in previous works. This report will mainly concentrate on: • determining the limit of validity of the theoretical model • evaluating the uncertainty of the experiments • investigating the quality of the interferometric measurement • trying to find out an appropriate way to measure 2D profiles • performing some 2D experiments and comparing the results to the theory Conclusions: • for the 1D case, the second order model appears to be quite well adapted as long as the ratio Tmax h∞ remains smaller than 2. For the 2D case, the linear model does not fit quantitatively with the experiments. A non linear theory should be elaborated. • the experimental set-up has been slightly modified to yield more accurate measurements, and with a better quality of images • improvements of the previous image processing software have been done. Nevertheless, an extension of this software to the 2D case turns out to be very tricky. An attempt of measurement by phase steping interferometry yielded conclusive results: such a method should be adapted to the present set-up. c Koninklijke Philips Electronics N.V. 2000 iii 833/99 Unclassified Report iv c Koninklijke Philips Electronics N.V. 2000 Unclassified Report 833/99