Characterization of the accuracy of EUV phase-shifting point diffraction interferometry

Naulleau, Patrick; Goldberg, Kenneth A.; Chang, Chang-Hasnain C.; Bresloff, Cynthia J.; Batson, Phillip J.; Attwood, David; Bokor, Jeffrey

doi:10.1117/12.309563

Cited by 20 publications

(13 citation statements)

References 6 publications

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“…For example, in speckle dynamics experiments [8] where coherent power is important but wavefront quality is typically not, it is evident that the Zernike approximation would significantly underestimate the usable beam size and power. We note, however, that for EUV point-diffraction interferometry [9,10], these issues are less important. In this case, the spatial-filtering pinhole placed at the focus of the beamline serves the dual purpose of improving the spatial coherence, and, more importantly, generating a highly spherical probe beam.…”

Section: Discussionmentioning

confidence: 85%

Analysis of illumination coherence properties in small-source systems such as synchrotrons

Chang¹,

Naulleau²,

Attwood³

2003

Appl. Opt.

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Modern synchrotron beamlines often take the form of critical illumination systems, where an incoherent source of limited spatial extent is re-imaged to an experimental plane of interest. Unique constraints of synchrotron sources and beamlines, however, may preclude the use of the simple Zernike approximation for calculating the object-image coherence relationship. Here, we perform a rigorous analysis of the object-image coherence relationship valid for synchrotron beamlines. The analysis shows beamline aberrations to have an effect on the coherence properties. Effects of various low-order aberrations on the coherence properties are explicitly studied.

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Section: Discussionmentioning

confidence: 85%

Analysis of illumination coherence properties in small-source systems such as synchrotrons

Chang¹,

Naulleau²,

Attwood³

2003

Appl. Opt.

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“…The phases of two complex amplitude maps correspond to the differential wavefronts of x-direction and y-direction, respectively. The differential Zernike polynomial fitting method was applied to retrieve the wavefront of CGLSI [5]. Annular Zernike polynomials are used in the process.…”

Section: Cglsi Methodsmentioning

confidence: 99%

“…When the CCD tilts as shown in Figure 6, it generates astigmatism in the PDI wavefront, however this translates into coma and 3θ components in CGLSI [5]. Therefore, we have to remove influence of CCD Tilt to compare CGLSI with PDI.…”

Section: Influence Of Ccd Tiltmentioning

confidence: 96%

Comparison of EUV interferometry methods in EUVA project

et al. 2005

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We are developing an at-wavelength interferometer for EUV lithography systems. The goal is the measurement of the wavefront aberration for a six-aspherical mirror projection optic. Among the six methods that EEI can measure, we selected CGLSI and PDI for comparison. PDI is a method well-known for its high accuracy, while CGLSI is a simple measurement method. Our comparison of PDI and CGLSI methods, verified the precision of the CGLSI method. The results show a difference between the methods of 0.33nm RMS for terms Z5-36. CGLSI measurement wavefronts agree well with PDI for terms Z5-36, and it is thought of as a promising method. Using FFT analysis, we estimated and then removed the impact of flare on the wavefront. As a result of having removed the influence of flare, the difference between CGLSI and PDI improved to only 0.26nm RMS in Zernike 5-36 terms. We executed PDI wavefront retrieval with FFT, which has not been used till now. By confirming that the difference between methods using FFT and Phase shift is 0.035nm RMS for terms Z5-36, we have proven that PDI wavefront analysis with FFT is possible.

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“…Due to the accuracy limitation of standard optics, the traditional interferometers fail to measure the point-diffraction wavefront error, which is expected to be in the order of subnanometer or even smaller. Various experimental testing methods have been proposed to measure the point-diffraction wavefront error, the majority of which are based on the hybrid method [15] and null test [28]. Typically, the hybrid method requires several measurements with the rotation and displacement of the optics under test, it is sensitive to environmental disturbance and cannot completely separate the systematic error.…”

Section: Experimental Measurement Of Point-diffraction Wavefrontmentioning

confidence: 99%

Point Diffraction Interferometry

Wang¹,

Liang²

2017

Optical Interferometry

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The point diffraction interferometer (PDI) employs a point-diffraction spherical wavefront as ideal measurement reference, and it overcomes the accuracy limitation of reference optics in traditional interferometers. To overcome the limitation of measurement range either with pinhole (low light transmission) or with single-mode fiber (low NA), a single-mode fiber with narrowed exit aperture has been proposed to obtain the point-diffraction wavefront with both high NA and high power. It is a key issue to analyze the point-diffraction wavefront error in PDI, which determines the achievable accuracy of the system. The FDTD method based on the vector diffraction theory provides a powerful tool for the design and optimization of the PDI system. In addition, a high-precision method based on shearing interferometry can be applied to measure point-diffraction wavefront with high NA, in which a double-step calibration including three-dimensional coordinate reconstruction and symmetric lateral displacement compensation is used to calibrate the geometric aberration. The PDI is expected to be a powerful tool for high-precision optical testing. With the PDI method, a high accuracy with RMS value better than subnanometer can be obtained in the optical surface testing and submicron in the absolute three-dimensional coordinate measurement, demonstrating the feasibility and wide application foreground of PDI.

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Characterization of the accuracy of EUV phase-shifting point diffraction interferometry

Cited by 20 publications

References 6 publications

Analysis of illumination coherence properties in small-source systems such as synchrotrons

Analysis of illumination coherence properties in small-source systems such as synchrotrons

Comparison of EUV interferometry methods in EUVA project

Point Diffraction Interferometry

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