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Interferometric at-wavelength flare characterization of EUV optical systems

Patent ·
OSTI ID:873741
 [1];  [2]
  1. Oakland, CA
  2. Berkeley, CA
+ Show Author Affiliations

The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) provides the high-accuracy wavefront characterization critical to the development of EUV lithography systems. Enhancing the implementation of the PS/PDI can significantly extend its spatial-frequency measurement bandwidth. The enhanced PS/PDI is capable of simultaneously characterizing both wavefront and flare. The enhanced technique employs a hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI. Using the dual-domain technique in combination with a flare-measurement-optimized mask and an iterative calculation process for removing flare contribution caused by higher order grating diffraction terms, the enhanced PS/PDI can be used to simultaneously measure both figure and flare in optical systems.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA
DOE Contract Number:
AC03-76SF00098
Assignee:
Regents of University of California (Oakland, CA)
Patent Number(s):
US 6233056
OSTI ID:
873741
Country of Publication:
United States
Language:
English

References (5)

Multichannel phase-shifted interferometer journal January 1984
Liquid-crystal point-diffraction interferometer journal January 1994
Phase-shifting point diffraction interferometer journal January 1996
Progress towards λ/20 extreme ultraviolet interferometry journal November 1995
Theory and Application of Point-Diffraction Interferometers journal January 1975

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at-wavelength
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dual-domain
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