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Proceedings Paper

Coherent Fourier scatterometry: tool for improved sensitivity in semiconductor metrology
Author(s): N. Kumar; O. El Gawhary; S. Roy; V. G Kutchoukov; S. F. Pereira; W. Coene; H. P. Urbach
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Paper Abstract

Incoherent Optical Scatterometry (IOS) is a well-established metrology technique in the semiconductor industry to retrieve periodic grating structures with high accuracy from the signature of the diffracted optical far field. With shrinking dimensions in the lithography industry, finding possible improvements in wafer metrology is highly desirable. The grating is defined in terms of a finite number of geometrical shape parameters (height, side-wall angles, midCD etc.). In our method the illumination is a scanning focused spot from a spatially coherent source (laser) within a single period of the grating. We present a framework to study the increment in sensitivity of Coherent Fourier Scatterometry (CFS) with respect to the IOS. Under suitable conditions, there is a more than fourfold enhancement in sensitivity for grating shape parameters using CFS. The dependence of scanning positions on the sensitivity analysis is also highlighted. We further report the experimental implementation of a Coherent Fourier Scatterometer. The simulated and experimental far fields are compared and analyzed for the real noise in the experimental configuration.

Paper Details

Date Published: 3 April 2012
PDF: 8 pages
Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83240Q (3 April 2012); doi: 10.1117/12.916357
Show Author Affiliations
N. Kumar, Technische Univ. Delft (Netherlands)
O. El Gawhary, Technische Univ. Delft (Netherlands)
S. Roy, Technische Univ. Delft (Netherlands)
V. G Kutchoukov, Technische Univ. Delft (Netherlands)
S. F. Pereira, Technische Univ. Delft (Netherlands)
W. Coene, ASML Netherlands B.V. (Netherlands)
H. P. Urbach, Technische Univ. Delft (Netherlands)

Published in SPIE Proceedings Vol. 8324:
Metrology, Inspection, and Process Control for Microlithography XXVI
Alexander Starikov, Editor(s)

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