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Critical dimension metrology using optical diffraction microscopy
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Paper Abstract

We present an innovative method Optical Diffraction Microscopy (ODM). for the simultaneous measurement of specular and non-specular diffraction patterns of sub-micron periodic structures. A sample is illuminated with broadband light and the diffraction pattern is collected by using a pair of ellipsoidal mirrors, optical fibers and a spectrometer. This method allows for rapid measurements and makes used of the Rigorous Coupled Wave algorithm for data analysis. In the present work the method has been applied to binary and multi-layer sub-micron gratings. A series of binary gratings with periods of 318 nm and 360 nm with different exposure levels of the photoresist were investigated. We succeded in characterize underexposed, ideally exposed and overexposed photoresist grating profiles. The measurements are well-suited to determine the delivered exposure energy density to photoresist gratings. The ODM technique may thus be applied to specify the exposure window and as a feedback in order to adjust the exposure energy density on-line. The homogeneity of a grating on multi-layered substrate has been investigated. Heights and duty cycles ranging from 50 nm to 55 nm and 0.25 to 0.97, respectively, have been found. AFM measurements of the gratings verify the ODM results and demonstrate that the ODM technique can be used to determine grating topology.

Paper Details

Date Published: 19 October 2005
PDF: 11 pages
Proc. SPIE 5965, Optical Fabrication, Testing, and Metrology II, 596508 (19 October 2005); doi: 10.1117/12.624769
Show Author Affiliations
Niels Agersnap, LuKa OptoScope (Denmark)
Poul-Erik Hansen, LuKa OptoScope (Denmark)
Jan Conrad Petersen, Danish Fundamental Metrology (Denmark)
Jørgen Garnæs, Danish Fundamental Metrology (Denmark)
Nathalie Destouches, Univ. of Saint-Etienne (France)
Olivier Parriaux, Univ. of Saint-Etienne (France)

Published in SPIE Proceedings Vol. 5965:
Optical Fabrication, Testing, and Metrology II
Angela Duparré; Roland Geyl; Lingli Wang, Editor(s)

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