Measuring method for optical fiber diffraction reference wavefront deviations of optical fiber point diffraction interferometer

Abstract

The invention discloses a measuring method for optical fiber diffraction reference wavefront deviations of an optical fiber point diffraction interferometer and relates to the technical field of optical measurement. According to the measuring method, a four-optical-fiber shearing mode or a two-optical-fiber rotating mode is adopted to evaluate deviations of optical fiber diffraction reference wavefront in two orthogonal directions, so that inspection on the optical fiber diffraction reference wavefront is completed experimentally, and difficulty in measurement of the optical fiber diffraction reference wavefront deviations is overcome. By means of subjecting two spherical waves produced by optical diffraction to shearing interference in the two orthogonal directions perpendicular to each other, the deviations in the two orthogonal directions at the front edge of the optical fiber diffraction reference wavefront can be obtained from a shearing interference pattern, requirements of higher-precision detection equipment are met, and the deficiency in evaluating the optical fiber diffraction reference wavefront deviation in a single direction is overcome.

Description

technical field [0001] The invention relates to the technical field of optical measurement, in particular to a method for measuring the deviation of a high-precision reference wavefront of optical fiber diffraction by an optical fiber point diffraction interferometer. Background technique [0002] Extreme Ultraviolet Lithography (EUVL) is a photolithography process suitable for the manufacture of several generations of ultra-large-scale integrated circuits at 22nm and below. It uses an exposure wavelength of 13.5nm to image the circuit pattern on the mask onto the wafer. Because in the EUV band, the refractive index of various materials is close to 1, and the absorption is very large, the EUVL projection exposure objective lens system must adopt a total reflection optical system composed of optical aspheric surfaces coated with multi-layer films. [0003] In order to make the graphics on the mask nearly perfect on the wafer, the projection exposure objective lens system is r...

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Problems solved by technology

[0005] As the highest precision interferometer that can be achieved at present, the point diffraction interferometer has a higher precision of the diffraction reference wavefront than itself. direct measurement of the mass of the

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