Phase measurements of EUV mask defects

Extreme Ultraviolet (EUV) Lithography mask defects were examined on the actinic mask imaging system, SHARP, at Lawrence Berkeley National Laboratory. A quantitative phase retrieval algorithm based on the Weak Object Transfer Function was applied to the measured through-focus aerial images to examine...

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Bibliographic Details
Main Authors: Claus, Rene A, Wang, Yow-Gwo, Wojdyla, Antoine, Benk, Markus P, Goldberg, Kenneth A, Neureuther, Andrew R, Naulleau, Patrick P, Waller, Laura
Format: Conference Proceeding
Language:English
Subjects:
apertures
ENGINEERING
extreme ultraviolet
imaging systems
lithography
microscopes
phase contrast
phase measurement
phase retrieval
zone plates
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Summary:Extreme Ultraviolet (EUV) Lithography mask defects were examined on the actinic mask imaging system, SHARP, at Lawrence Berkeley National Laboratory. A quantitative phase retrieval algorithm based on the Weak Object Transfer Function was applied to the measured through-focus aerial images to examine the amplitude and phase of the defects. The accuracy of the algorithm was demonstrated by comparing the results of measurements using a phase contrast zone plate and a standard zone plate. Using partially coherent illumination to measure frequencies that would otherwise fall outside the numerical aperture (NA), it was shown that some defects are smaller than the conventional resolution of the microscope. Programmed defects of various sizes were measured and shown to have both an amplitude and a phase component that the algorithm is able to recover.
ISSN:0277-786X
0091-3286
1560-2303
DOI:10.1117/12.2087195