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Proceedings Paper

Interferometry of thick and thin films
Author(s): Michael Conroy
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Paper Abstract

Interferometry is now an established technique for the measurement of surface topography. It has the capability of combining sub-nanometre resolution. A very useful extension to its capability is the ability to measure thick and thin films on a local scale. For films with thicknesses in excess of 1-2μm (depending on refractive index), the SWLI interaction with the film leads simply the formation of two localised fringes, each corresponding to a surface interface. It is relatively trivial to locate the positions of these two envelope maxima and therefore determine the film thickness, assuming the refractive index is known. For thin films (with thicknesses ~20nm to ~2μm, again depending on the index), the SWLI interaction leads to the formation of a single interference maxima. In this context, it is appropriate to describe the thin film structure in terms of optical admittances; it is this regime that is addressed through the introduction of a new function, the 'helical conjugate field' (HCF) function. This function may be considered as providing a 'signature' of the multilayer measured so that through optimization, the thin film multilayer may be determined on a local scale.

Paper Details

Date Published: 18 June 2007
PDF: 9 pages
Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 661620 (18 June 2007); doi: 10.1117/12.726248
Show Author Affiliations
Michael Conroy, Taylor Hobson, Ltd. (United Kingdom)


Published in SPIE Proceedings Vol. 6616:
Optical Measurement Systems for Industrial Inspection V
Wolfgang Osten; Christophe Gorecki; Erik L. Novak, Editor(s)

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