Shearing Interferometry for at Wavelength Wavefront Measurement of Extreme-Ultraviolet Lithography Projection Optics

Zhu, Yongtian; Sugisaki, Katsumi; Murakami, Katsuhiko; Ota, Ken‐ichiro; Kondo, Hiroyuki; Ishii, Mikihiko; Kawakami, Jun; Oshino, Tetsuya; Saito, Jun; Suzuki, Atsushi; Hasegawa, Masanobu; Sekine, Yoshiyuki; Takeuchi, Shigeyuki; Ouchi, Chidane; Kakuchi, Osamu; Watanabe, Yutaka; Hasegawa, Takayuki; Hara, Shinichi

doi:10.1143/jjap.42.5844

Cited by 12 publications

(3 citation statements)

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“…In general, the shear ratios for different applications vary, for instance, it is usually 1% to 5% for measuring the wavefront aberration of high-precision imaging optics [20,28] and 10% to 20% for mirror surface figure measurements [1]. A larger shear ratio leads to higher measurement sensitivity, whereas a lower shear ratio can achieve a higher measurement dynamic range.…”

Section: Reconstruction Under Different Shear Ratiosmentioning

confidence: 99%

Modal wavefront reconstruction based on Zernike polynomials for lateral shearing interferometry: comparisons of existing algorithms

et al. 2012

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Four modal methods of reconstructing a wavefront from its difference fronts based on Zernike polynomials in lateral shearing interferometry are currently available, namely the Rimmer-Wyant method, elliptical orthogonal transformation, numerical orthogonal transformation, and difference Zernike polynomial fitting. The present study compared these four methods by theoretical analysis and numerical experiments. The results show that the difference Zernike polynomial fitting method is superior to the three other methods due to its high accuracy, easy implementation, easy extension to any high order, and applicability to the reconstruction of a wavefront on an aperture of arbitrary shape. Thus, this method is recommended for use in lateral shearing interferometry for wavefront reconstruction.

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Section: Reconstruction Under Different Shear Ratiosmentioning

confidence: 99%

Modal wavefront reconstruction based on Zernike polynomials for lateral shearing interferometry: comparisons of existing algorithms

et al. 2012

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“…Figure 2 (b) shows the PSLSI. 8 An aberration-free spherical wavefront is generated by diffraction of the 1st pinhole as in the PDI. The spherical wave is aberrated by the test optic.…”

Section: Ldimentioning

confidence: 99%

Comparisons between EUV at-wavelength metrological methods

Sugisaki

Okada

Zhu

et al. 2005

Advances in Metrology for X-Ray and EUV Optics

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“…However, a large lateral shear reduces the accuracy of wavefront reconstruction owing to the information lost during shearing 12 . The other unwanted orders could also be filtered out using a double-window mask, 13 – 15 and the complexity of the mechanical structure increased. Using sinusoidal or quasi-sinusoidal Ronchi gratings is another alternative method that could eliminate the higher diffractions 16 …”

Section: Introductionmentioning

confidence: 99%

Fast measurement of wavefront aberration in double-grating Ronchi lateral shearing interferometry

Tang

et al. 2023

Opt. Eng.

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The accuracy of the shear-phase retrieval method is critical for accurate wavefront aberration measurements in double-grating Ronchi lateral shearing interferometry. Currently, the suppression of the interferences of unwanted diffractions generated by the Ronchi grating at the image plane is eliminated by adding more phase shifts, which increases the measurement time.Here, a stepped phase-shifting algorithm is proposed to suppress the unwanted diffractions and retrieve the shear phase between AE1st orders accurately with fewer phase shifts, and the measurement efficiency can be increased by 25% at least. The minimum number of phase shifts, which depends on the high diffraction orders existing in the interferograms, is analyzed. The proposed method was verified via numerical simulations and experiments. The wavefront measurement was validated via a comparison with the results of point-diffracted interferometry, and the root-mean-square difference was within 2.0 nm.

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Shearing Interferometry for at Wavelength Wavefront Measurement of Extreme-Ultraviolet Lithography Projection Optics

Cited by 12 publications

References 1 publication

Modal wavefront reconstruction based on Zernike polynomials for lateral shearing interferometry: comparisons of existing algorithms

Modal wavefront reconstruction based on Zernike polynomials for lateral shearing interferometry: comparisons of existing algorithms

Comparisons between EUV at-wavelength metrological methods

Fast measurement of wavefront aberration in double-grating Ronchi lateral shearing interferometry

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