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Proceedings Paper

Zernike phase contrast microscope for EUV mask inspection
Author(s): Yow-Gwo Wang; Ryan Miyakawa; Andrew Neureuther; Patrick Naulleau
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Paper Abstract

In this paper, we address a new inspection method which provides in-focus inspection capability and higher defect sensitivity compared with conventional mask inspection methods. In the Zernike phase contrast microscope, an added phase shift to background wave combines with the phase of bump and pit defects to achieve higher contrast at focus. If we use a centralized apodization to half the lens radius to further reduce the intensity of the phase-shifted background wave, the signal strength can be improved up to 6-fold of its original value. Simulation results further show that this apodization for a typical EUV mask power spectral density results in the noise decreasing in absolute level similar to the clear field reference signal. Thus large improvements in signal to noise ratios are possible with the Zernike phase contrast microscope type systems for EUV mask inspection applications.

Paper Details

Date Published: 17 April 2014
PDF: 8 pages
Proc. SPIE 9048, Extreme Ultraviolet (EUV) Lithography V, 904810 (17 April 2014); doi: 10.1117/12.2048180
Show Author Affiliations
Yow-Gwo Wang, Lawrence Berkeley National Lab. (United States)
Univ. of California, Berkeley (United States)
Ryan Miyakawa, Lawrence Berkeley National Lab. (United States)
Andrew Neureuther, Lawrence Berkeley National Lab. (United States)
Univ. of California, Berkeley (United States)
Patrick Naulleau, Lawrence Berkeley National Lab. (United States)

Published in SPIE Proceedings Vol. 9048:
Extreme Ultraviolet (EUV) Lithography V
Obert R. Wood II; Eric M. Panning, Editor(s)

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