Aberration measuring method for projection optical system with a variable numerical aperture in an exposure apparatus

Abstract

A method disclosed in this specification is an aberration measuring method in which a light flux converged by a condensing optical system is made incident on a optical system to be measured, the light flux that has passed through the optical system to be measured is reflected by a reflecting optical system having a center of curvature at a light convergence point on a light emergence side of the optical system to be measured is made incident on the optical system to be measure again, and wavefront aberration of the optical system to be measured is detected as interference fringes using the light flux that has passed through the optical system to be measured again. Measurement is carried out while changing the numerical aperture of the optical system to be measured to a numerical aperture larger than a numerical aperture in the actual use, thereby realizing highly precise measurement of the wavefront aberration all over the effective numerical aperture of the optical system to be measured.

Description

[0001] This application is a divisional of co-pending application Ser. No. 10 / 791,081, filed Mar. 1, 2004. [0002] This application claims a benefit of priority based on Japanese Patent Application No. 2003-062016, filed on Mar. 7, 2003, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to a method for measuring aberration, and particularly to an aberration measuring method for measuring wavefront aberration of an optical system such as a projection optical system for transferring a pattern on a mask onto a photosensitive substrate. Such a projection optical system is used for example, in a lithography process for exposing an article to be processed such as a single crystal substrate like a semiconductor wafer or a glass substrate used for a liquid crystal display (LCD). [0005] 2. Related Background Art [0006] In the process for manufacturing m...

AI Technical Summary

Benefits of technology

The present invention provides an aberration measuring method that can accurately measure the wavefront aberration of a lens over its entire effective numerical aperture. This is achieved by making a light flux incident on the lens, reflecting it by a reflecting optical system, and detecting the wavefront aberration of the lens as interference fringes using the reflected light. The method includes steps of setting the numerical aperture of the lens to a larger value than its actual use and measuring the wavefront aberration at this set numerical aperture. This invention allows for precise measurement of aberration in optical systems, which can be useful in various applications such as in the manufacturing of semiconductor devices.

Problems solved by technology

In recent years particularly, with rapid miniaturization of semiconductor devices, patterns beyond ordinary imaging performance are often required to be transferred, and the transferred patterns have become sensitive to aberrations of optical systems.

This makes aberration correction all the more difficult.

This will cause a considerable measurement error.

Consequently, an error of the wavefront aberration in the periphery of the pupil due to the spread of the diffracted light becomes larger.

However, that method is not desirable, since the interference fringes will be shifted on the CCD camera 1240 on account of eccentricity generated upon shifting the CCD camera 1240 and correction needs to be carried out in the wavefront aberration calculation area for every image height of the central coordinate.

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