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Proceedings Paper

Design optimization of phase-shifting point diffraction interferometer
Author(s): Ke Liu; Yanqiu Li
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Paper Abstract

The phase-shifting point diffraction interferometer (PS/PDI) is so far the most accurate measurement tool in atwavelength interferometry of projection optics for extreme ultraviolet lithography (EUVL). The complicate interrelationships between configuration parameters of PS/PDI call for an optimization to achieve high accuracy of PS/PDI. In this paper, a novel system-level modeling approach is proposed to optimize the parameters of PS/PDI designed for visible light (λ=632.8nm) concept proof experiment. The optimal reference pinhole size selection is performed by modeling pinhole spatial filtering effect using Diffraction-Based Beam Propagation (BPR) module of CODE V and in house software. The result shows that various pinhole diameters ranging from 1.6um to 2.2um should be used in our PS/PDI experiment. The test window size and grating duty cycle optimization, which is based on the spatial frequency domain analysis of PS/PDI, is conducted by modeling the entire PS/PDI system using Physical Optics Propagation (POP) module of Zemax and in house software. The optimal window size is approximately 62um for a given window-pinhole separation of 63.3um. The optimal duty cycle of grating is calculated to be 83% to obtain the maximum fringe contrast of 0.879.

Paper Details

Date Published: 27 January 2009
PDF: 7 pages
Proc. SPIE 7156, 2008 International Conference on Optical Instruments and Technology: Optical Systems and Optoelectronic Instruments, 71561W (27 January 2009); doi: 10.1117/12.806760
Show Author Affiliations
Ke Liu, Institute of Electrical Engineering (China)
Graduate Univ. of the Chinese Academy of Sciences (China)
Yanqiu Li, Institute of Electrical Engineering (China)
Beijing Institute of Technology (China)

Published in SPIE Proceedings Vol. 7156:
2008 International Conference on Optical Instruments and Technology: Optical Systems and Optoelectronic Instruments
Yunlong Sheng; Yongtian Wang; Lijiang Zeng, Editor(s)

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