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Proceedings Paper

Simulations of optical microscope images
Author(s): Thomas A. Germer; Egon Marx
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Paper Abstract

The resolution of an optical microscope is limited by the optical wavelengths used. However, there is no fundamental limit to the sensitivity of a microscope to small differences in any of a feature's dimensions. That is, those limits are determined by such things as the sensitivity of the detector array, the quality of the optical system, and the stability of the light source. The potential for using this nearly unbounded sensitivity has sparked interest in extending optical microscopy to the characterization of sub-wavelength structures created by photolithography and using that characterization for process control. In this paper, an analysis of the imaging of a semiconductor grating structure with an optical microscope will be presented. The analysis includes the effects of partial coherence in the illumination system, aberrations of both the illumination and the collection optics, non-uniformities in the illumination, and polarization. It can thus model just about any illumination configuration imaginable, including Koehler illumination, focused (confocal) illumination, or dark-field illumination. By propagating Jones matrices throughout the system, polarization control at the back focal planes of both illumination and collection can be investigated. Given a detailed characterization of the microscope (including aberrations), images can be calculated and compared to real data, allowing details of the grating structure to be determined, in a manner similar to that found in scatterometry.

Paper Details

Date Published: 24 March 2006
PDF: 11 pages
Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61520I (24 March 2006); doi: 10.1117/12.656370
Show Author Affiliations
Thomas A. Germer, National Institute of Standards and Technology (United States)
Egon Marx, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 6152:
Metrology, Inspection, and Process Control for Microlithography XX
Chas N. Archie, Editor(s)

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