23 May 2011 Geometry reconstruction for scatterometry on a MoSi photo mask based on maximum likelihood estimation
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Abstract
Previous work has shown that the reconstruction of geometric parameters describing the profile of an attenuated phase shift (MoSi) photomask is possible by a least-square minimization of the difference between measurement data and simulation results. Modelling work on other related systems, in particular EUV scatterometry, has revealed a strong influence of the uncertainties assigned to the input data. Their choice may introduce a systematic bias to the determination of the reconstructed geometric quantities like line height, top- and bottom CDs or side-wall angles. Here we employ a maximum likelihood estimation (MLE) to obtain the profile parameters as well as consistent uncertainty estimates for the input data. The method is applied to a set of goniometric scatterometry measurements at a wavelength of 193nm on a state-of-the-art MoSi mask.
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M.-A. Henn, H. Gross, M. Bär, M. Wurm, B. Bodermann, "Geometry reconstruction for scatterometry on a MoSi photo mask based on maximum likelihood estimation", Proc. SPIE 8083, Modeling Aspects in Optical Metrology III, 808306 (23 May 2011); doi: 10.1117/12.895027; https://doi.org/10.1117/12.895027
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