25 September 2008 Extraction of film interface surfaces from scanning white light interferometry
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Abstract
In the field of scanning white light interferometry (SWLI), it is well known that films of optical thickness in excess of the coherence length may be measured by simply taking advantage of the fact that such films exhibit interference maxima corresponding to each interface. In fact for the majority of such 'thick' films the determined thickness has a DC error arising from the spectral phase-change on reflection at the two interfaces. For thinner films, the interference maxima coalesce and it was for this regime that the HCF (helical complex field) was previously introduced to allow thin film extraction. This work has now been significantly extended with a demonstrated capability to extract film interfaces with a lateral (XY) resolution of 1.25μm and a (Z) surface rms noise of ~0.75A (angstrom). It is also capable of covering both the thin and thick film regimes (from ~50nm to several microns, both limits being material dependant). Results are presented showing the performance of this approach, these include 'micro-scratches' that are apparent in the thickness of the deposited layers as well as substrate/film and film/air interfaces. These are compared to the original 'surface' as determined by SWLI and by AFM surface measurements. Additionally a brief comparison is made between film thickness determination using this approach, spectrophotometry, ellipsometry and stylus profilometry.
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Daniel Mansfield, "Extraction of film interface surfaces from scanning white light interferometry", Proc. SPIE 7101, Advances in Optical Thin Films III, 71010U (25 September 2008); doi: 10.1117/12.797978; https://doi.org/10.1117/12.797978
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