Polarization control method used in fiber point-diffraction interferometer wave surface reference source

Abstract

The invention relates to a polarization control method used in a fiber point-diffraction interferometer wave surface reference source. The polarization control method includes the steps that optical fiber diffraction spherical wave is collimated through a high-quality collimator lens, and then passes through a rotatable polarizing film placed on a single-axis displacement platform, a double-layer density disk located in a through hole, a pentaprism, and an optical power meter, wherein the pentaprism and the optical power meter are placed on the single-axis displacement platform, and the polarization state of an initial light beam can be determined by theoretical calculation through the rotatable polarizing film; the rotatable polarizing film is then moved out of the light path through the single-axis displacement platform, the double-layer density disk is turned to be in the circularly polarized light detection state, namely, a 1 / 4 wave plate and a polarizing film, the control voltages of two control channels of a polarization controller are calculated through the polarization state of the initial light beam, which is obtained in the previous step, and then the circular polarization state is obtained through fine adjustment and observation of the optical power meter reading till extinction. The system has the advantages of being capable of achieving quick adjustment of the circular polarization state under the premise that extra error is not introduced to the wave surface reference source and effectively improving contrast ratio and detection precision of interference fringe.

Description

technical field [0001] The invention belongs to the field of polarization control of a point-diffraction interferometer wave-front reference source, and in particular relates to a polarization control method used in a fiber-optic point-diffraction interferometer wave-front reference source. Background technique [0002] Extreme ultraviolet lithography (EUVL) technology is considered to be one of the most promising next-generation lithography technologies. It uses 13.5nm extreme ultraviolet light to image the pattern on the mask on a silicon wafer coated with photoresist. , in order to achieve the resolution of the diffraction limit of the projection optical system, according to the Marachel criterion, the wave aberration of the system is required to be less than λ / 14, that is, 1nm RMS, so the wave aberration detection device of the projection system must achieve sub-nanometer precision, and the traditional interference The detection method has been unable to realize the high...

AI Technical Summary

Problems solved by technology

[0003] The present invention aims to solve the technical problems in the prior art and meet the requirements of the point diffraction interferometer used in extreme ultraviolet lithography optical detection for the circular polarization state of the diffracted wavefront, that is, to quickly realize the circular polarization state without introducing additional errors Regulation, providing a polarization control method used in the wavefront reference source of the fiber point diffraction interferometer

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