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Proceedings Paper

Toward sub-0.1-um CD measurements using scatterometry
Author(s): Babar K. Minhas; Steven L. Prins; S. Sohail H. Naqvi; John Robert McNeil
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Paper Abstract

Scatterometry, defined as the angle resolved characterization of light scattered from a surface, is an attractive tool for the metrology of semiconductor devices. It is simple, rapid, non destructive, relatively inexpensive and can be used in-situ. This paper illustrates the use of scatterometry to characterize fine pitch gratings having linewidths less than or equal to 0.1 micrometer. These gratings diffract light only in the zeroth order as their pitch-to-wavelength ratio is much smaller than one, hence they are also known as 0-order gratings. Metrology of 0-order gratings brings forth new issues, chiefly (1) lack of diffraction sensitivity to variation in the grating parameters, and (2) non-uniqueness of the 'diffraction signatures.' We use the gratings in conical mounting to enhance the diffraction sensitivity and have circumvented the non-uniqueness issue in two ways: (1) limiting the parameter space of the search algorithm and (2) using different incident field polarizations. We employ constrained optimization techniques to efficiently scan the parameter space. Our results agree well with cross-sectional SEM measurements and demonstrate the feasibility of scatterometry for these structures. We are also using shorter wavelengths for the metrology of 0-order gratings, and preliminary results using (lambda) equals 442 nm demonstrate that the diffraction is more sensitive to the variation in grating linewidth and etch depth.

Paper Details

Date Published: 21 May 1996
PDF: 11 pages
Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996);
Show Author Affiliations
Babar K. Minhas, Univ. of New Mexico (United States)
Steven L. Prins, Univ. of New Mexico (United States)
S. Sohail H. Naqvi, Univ. of New Mexico (United States)
John Robert McNeil, Univ. of New Mexico (United States)

Published in SPIE Proceedings Vol. 2725:
Metrology, Inspection, and Process Control for Microlithography X
Susan K. Jones, Editor(s)

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