A catadioptric objective lens

Abstract

The invention discloses a catadioptric objective lens for imaging a figure in an object plane into an image plane. The catadioptric objective lens includes a first mirror group, a second mirror group and a third mirror group in order from the object plane side to the image plane side along the optical axis direction. The first mirror group and the second mirror group have positive focal power, the first mirror group is a catadioptric mirror group having at least two catadioptric surfaces and at least two reflection surfaces, and the central parts of the at least two reflection surfaces of the catadioptric mirror group have no reflectivity and allow light to pass through. The light emitted by the object plane forms an intermediate image after passing through the first mirror group, and the intermediate image passes through the second mirror group and the third mirror group before being imaged to the image plane, and the relationship of 1.2 <| Rm | / f1 <3.2 is satisfied, where f1 is the combined focal length of the first mirror group, and Rm is the radius of curvature of the reflection surface with the smallest radius of curvature of all the reflection surfaces of the first mirror group. The catadioptric objective lens can effectively correct various aberrations of a large-aperture system, especially advanced spherical aberration.

Description

technical field [0001] The invention relates to a wide-spectrum catadioptric objective lens, in particular to a catadioptric objective lens with wide-spectrum high-resolution, large field of view and high magnification, which is used in the deep ultraviolet wavelength range of 200nm to 350nm. Background technique [0002] As the integration density of semiconductor chips and devices increases, the inspection optical system is required to have high resolution in order to detect more precise details. In order to improve the resolution of the inspection optical system, the optical system is required to use shorter wavelength illumination light, and the numerical aperture of the detection objective lens is required to be larger. In the ultraviolet wavelength region, especially the deep ultraviolet wavelength region from 200nm to 350nm, ordinary optical materials have great absorption and low light transmittance. As the numerical aperture increases, it becomes difficult to corre...

AI Technical Summary

Problems solved by technology

As the numerical aperture increases, it is also difficult to correct aberrations using only refractive optics

[0003] With the development of detection technology, the requirements and requirements for high-resolution and large-field optical detection are increasing, and the design and manufacture of objective lenses with wide-spectrum, high-resolution, and large-field performance are very difficult, and there are few precedents at present.

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