Catadioptric reduction projection optical system and exposure apparatus having the same

Abstract

A catadioptric projection optical system is provided, which can use a beam splitting optical system smaller in size than a conventional polarizing beam splitter, can set a long optical path from a concave reflecting mirror to an image plane, allows easy adjustment of the optical system, and has excellent imaging performance. A light beam from an object surface forms a first intermediate image through a refracting lens group. A light beam from the first intermediate image passes through a polarizing beam splitter and is reflected by a concave reflecting mirror to form a second intermediate image in the polarizing beam splitter. A light beam from the second intermediate image is reflected by the polarizing beam splitter means to form a final image on the image plane via a refracting lens group. The polarizing beam splitter means is arranged near the positions at which the intermediate images are formed.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a catadioptric reduction optical system suitably applied to a projection optical system for reduction projection in a projection exposure apparatus of a one-shot exposure method or a scanning exposure method, used to manufacture a semiconductor element or a liquid crystal display element in a photolithographic process and, more particularly, to a catadioptric reduction projection optical system having a magnification of about 1 / 4 to 1 / 5 with a resolution on the submicron order in the ultraviolet wavelength range.2. Related Background ArtIn fabricating semiconductor devices or liquid crystal display devices, etc. by photolithography process, the projection exposure apparatus is used for demagnifying through a projection optical system a pattern image on a reticle (or photomask, etc.) for example at a ratio of about 1 / 4 to 1 / 5 to effect exposure of the image on a wafer (or glass plate, etc.) coated wi...

AI Technical Summary

Benefits of technology

The present invention has as its object to provide a catadioptric reduction projection optical system which can use a beam splitting optical system smaller in size than a conventional polarizing beam splitter, can set a long optical path from a concave reflecting mirror to the image plane, can easily adjust the optical system, and has excellent imaging performance.

In applying the present invention to an exposure apparatus, in order to prevent a change in magnification with variations in image plane, at which a wafer or the like is located, in the optical axis direction, a telecentric state is preferably ensured at least on the image plane side.

Problems solved by technology

If, however, the exposure wavelength is shortened, the types of optical glass which can be used in practice are limited because of the absorption of illumination light.

The difference between the Abbe constants of the synthetic quartz and the fluorite is not large enough to correct chromatic aberration.

For this reason, if the exposure wavelength becomes 300 nm or less, and a projection optical system is constituted by only a refracting optical system, chromatic aberration correction is very difficult to perform.

In addition, since fluorite undergoes a considerable change in refractive index with a change in temperature, i.e., has poor temperature characteristics, and involves many problems in a lens polishing process, fluorite cannot be used for many portions.

It is, therefore, very difficult to form a projection optical system having a required solution by using only a refracting system.

In this case, however, the projection optical system increases in size and requires aspherical reflecting surfaces.

It is very difficult to manufacture large, high-precision, aspherical surfaces

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