27 April 1999 Modeling of optical scatterometry with finite-number-of-periods gratings
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Optical scatterometry (OS) is a promising new technique for the in-line metrology of submicron features since it is non- invasive, rapid and highly accurate for multiparametric CD- measurements of submicon features. A serious drawback of the method is the need for relative large periodic areas to measure at. This is caused by the underlying model of plane- wave incidence. In this paper, the reduction of the measuring field to a few square microns is proposed. In this case, the diffraction of a focussed beam from a grating with a finite number of periods has to be investigated. This is done by means of rigorous modeling. One of the most essential outcomes is that, while increasing the number of covered grating periods with a wider beam, the integrated diffraction efficiency approaches very quickly the value obtained with plane wave diffraction on an infinite grating. Besides, it can be shown that both - a lateral shift as well as a moderate defocusing have negligible impact even at very small beam diameters. In addition, an effective model was developed for the efficient simulation of 2(theta) - scatterometry on FNPs.
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Joerg Bischoff, Joerg Bischoff, Karl Hehl, Karl Hehl, } "Modeling of optical scatterometry with finite-number-of-periods gratings", Proc. SPIE 3743, In-Line Characterization, Yield Reliability, and Failure Analyses in Microelectronic Manufacturing, (27 April 1999); doi: 10.1117/12.346935; https://doi.org/10.1117/12.346935

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