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Modeling the Effect of Finite Size Gratings on Scatterometry Measurements



Elizabeth Kenyon, Michael W. Cresswell, Heather Patrick, Thomas Germer


The interpretation of scatterometry measurements generally assumes that the grating extends over an area large enough to intercept all the illumination provided by an incident beam. However, in practice, the gratings used in scatterometry are relatively small. Thus, the detected light also includes both that scattered by the grating as well as that from a region surrounding the grating because, generally, the incident beam illuminates both the grating and the surrounding region. To model the effects of such real structures, simulations of the effective reflectance were performed whereby the reflection from the grating was considered to be the sum of the diffraction by the grating and the diffraction of the surrounding region, taking into account the beam profile. To demonstrate the model, the illumination field was assumed to be Gaussian. Results are shown for a specific target design consisting of a 50 m square measured by normal incidence reflectometry. Significant errors occur when the incident profile has wings that fall outside of the profile and when the scattered light is partially apertured.
Conference Dates
February 25, 2008
Conference Location
San Jose, CA
Conference Title
Proceedings of the SPIE, Volume 6922


critical dimension, diffraction, gratings, metrology, process control, scatterometry, standards


Kenyon, E. , Cresswell, M. , Patrick, H. and Germer, T. (2008), Modeling the Effect of Finite Size Gratings on Scatterometry Measurements, Proceedings of the SPIE, Volume 6922, San Jose, CA, [online], (Accessed April 17, 2024)
Created August 31, 2008, Updated October 12, 2021