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10 May 2005 Double-grating lateral shearing interferometer for EUV optics at-wavelength measurement
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A Calibration technology for double-grating lateral shearing interferometer1 (DLSI) and lateral shearing interferometer (LSI) is proposed in this paper. In this method, two measurements are used for calibration. One is the measurement by using the first- and zero-order diffraction beams of grating in the interferometer; the other one is the measurement by using the minus-first-order and zero-order diffraction beams. The phase distributions were calculated out from the two measurements. After shifted one phase distribution to superpose the other one, in the sum of the two phase distributions, the test wavefront is canceled. The system error caused by the grating diffraction and grating tilt can be calculated out from the sum of the superposed phase distributions. For calculating out the system errors, the sum of the two phase distributions is fitted to Zernike-Polynomials. From the coefficients of the Zernike-polynomials, the system error is calculated. This method is carried out to calibrate the system error of DLSI. We performed an experiment to verify the available of our calibration method.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Zhiqiang Liu, Masashi Okada, Katsumi Sugisaki, Mikihiko Ishii, Yucong Zhu, Katsura Ohtaki, Jun Saito, Akiyoshi Suzuki, Masanobu Hasegawa, Chidane Ouchi, Seima Kato, Masahito Niibe, and Katsuhiko Murakami "Double-grating lateral shearing interferometer for EUV optics at-wavelength measurement", Proc. SPIE 5752, Metrology, Inspection, and Process Control for Microlithography XIX, (10 May 2005);

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