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Title: Phase-shifting point-diffraction interferometry at EUV wavelengths

Abstract

A novel phase-shifting point-diffraction interferometer (PS/PDI) operating at the Advanced Light Source (ALS) is being used to perform wavefront-measuring metrology at 13.4-nm wavelength to characterize aberrations in a multilayer-coated 10x Schwarzschild objective designed for extreme ultraviolet (EUV) projection lithography experiments. To achieve 0.1-micron critical dimension pattern transfer with EUV projection lithography at 13.4-nm wavelength, nearly diffraction-limited all-reflective multilayer-coated optical systems with 0.1 numerical aperture are required. The EUV wavefront, determined by the mirror surfaces and the reflective multilayer coatings, is measurable only at the operational wavelength of the system. The authors goal is to measure the EUV wavefront to an accuracy of 0.01 waves rms (0.13 nm). The PS/PDI is a type of point-diffraction interferometer, modified for significantly improved throughput and phase-shifting capability. The interferometer design utilizes a grating beamsplitter and pinhole spatial filters in the object and image planes of the optical system under test. The 10x-reduction Schwarzschild objective, with image-side numerical aperture of 0.08, is illuminated by a sub-micron pinhole in the object plane. A coarse, 20-micron pitch grating placed between the illumination pinhole and the Schwarzschild system serves a dual role as a small-angle beam-splitter and a phase-shifting element. The first-order diffracted beam from the grating ismore » spatially filtered in the image plane of the Schwarzschild with a sub-100-nm pinhole and becomes the `D reference` wave in the interferometer. The zero-order beam is the `test` wave, and it passes unobstructed through a 4.5-{mu}m window in the image plane. The test and reference beams are separated by several microns in the image plane to minimize beam overlap. The interference fringes are recorded with a CCD detector placed about 12 cm from the Schwarzschild image plane.« less

Authors:
; ;  [1]
  1. Ernest Orlando Lawrence Berkeley National Lab., CA (United States); and others
Publication Date:
Research Org.:
Lawrence Berkeley Lab., CA (United States)
OSTI Identifier:
603707
Report Number(s):
LBNL-39981
ON: DE97007345; TRN: 98:009628
DOE Contract Number:  
AC03-76SF00098
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Apr 1997; Related Information: Is Part Of Advanced light source: Compendium of user abstracts 1993--1996; PB: 622 p.
Country of Publication:
United States
Language:
English
Subject:
44 INSTRUMENTATION, INCLUDING NUCLEAR AND PARTICLE DETECTORS; EXTREME ULTRAVIOLET RADIATION; INTERFEROMETRY; PHASE SHIFT; OPTICAL SYSTEMS; MEASURING METHODS

Citation Formats

Goldberg, K. A., Tejnil, E., and Lee, Sang. Phase-shifting point-diffraction interferometry at EUV wavelengths. United States: N. p., 1997. Web. doi:10.2172/603707.
Goldberg, K. A., Tejnil, E., & Lee, Sang. Phase-shifting point-diffraction interferometry at EUV wavelengths. United States. https://doi.org/10.2172/603707
Goldberg, K. A., Tejnil, E., and Lee, Sang. Tue . "Phase-shifting point-diffraction interferometry at EUV wavelengths". United States. https://doi.org/10.2172/603707. https://www.osti.gov/servlets/purl/603707.
@article{osti_603707,
title = {Phase-shifting point-diffraction interferometry at EUV wavelengths},
author = {Goldberg, K. A. and Tejnil, E. and Lee, Sang},
abstractNote = {A novel phase-shifting point-diffraction interferometer (PS/PDI) operating at the Advanced Light Source (ALS) is being used to perform wavefront-measuring metrology at 13.4-nm wavelength to characterize aberrations in a multilayer-coated 10x Schwarzschild objective designed for extreme ultraviolet (EUV) projection lithography experiments. To achieve 0.1-micron critical dimension pattern transfer with EUV projection lithography at 13.4-nm wavelength, nearly diffraction-limited all-reflective multilayer-coated optical systems with 0.1 numerical aperture are required. The EUV wavefront, determined by the mirror surfaces and the reflective multilayer coatings, is measurable only at the operational wavelength of the system. The authors goal is to measure the EUV wavefront to an accuracy of 0.01 waves rms (0.13 nm). The PS/PDI is a type of point-diffraction interferometer, modified for significantly improved throughput and phase-shifting capability. The interferometer design utilizes a grating beamsplitter and pinhole spatial filters in the object and image planes of the optical system under test. The 10x-reduction Schwarzschild objective, with image-side numerical aperture of 0.08, is illuminated by a sub-micron pinhole in the object plane. A coarse, 20-micron pitch grating placed between the illumination pinhole and the Schwarzschild system serves a dual role as a small-angle beam-splitter and a phase-shifting element. The first-order diffracted beam from the grating is spatially filtered in the image plane of the Schwarzschild with a sub-100-nm pinhole and becomes the `D reference` wave in the interferometer. The zero-order beam is the `test` wave, and it passes unobstructed through a 4.5-{mu}m window in the image plane. The test and reference beams are separated by several microns in the image plane to minimize beam overlap. The interference fringes are recorded with a CCD detector placed about 12 cm from the Schwarzschild image plane.},
doi = {10.2172/603707},
url = {https://www.osti.gov/biblio/603707}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1997},
month = {4}
}