23 May 2011 Modeling of profilometry with laser focus sensors
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Abstract
Metrology is of paramount importance in submicron patterning. Particularly, line width and overlay have to be measured very accurately. Appropriated metrology techniques are scanning electron microscopy and optical scatterometry. The latter is non-invasive, highly accurate and enables optical cross sections of layer stacks but it requires periodic patterns. Scanning laser focus sensors are a viable alternative enabling the measurement of non-periodic features. Severe limitations are imposed by the diffraction limit determining the edge location accuracy. It will be shown that the accuracy can be greatly improved by means of rigorous modeling. To this end, a fully vectorial 2.5-dimensional model has been developed based on rigorous Maxwell solvers and combined with models for the scanning and various autofocus principles. The simulations are compared with experimental results. Moreover, the simulations are directly utilized to improve the edge location accuracy.
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Jörg Bischoff, Eberhard Manske, Henner Baitinger, "Modeling of profilometry with laser focus sensors", Proc. SPIE 8083, Modeling Aspects in Optical Metrology III, 80830C (23 May 2011); doi: 10.1117/12.888195; https://doi.org/10.1117/12.888195
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