Refraction and reflection projection optical system

Abstract

The invention provides a diffractive-refractive projection optical system, which is used for projecting the image of a pattern disposed in an object plane into an image plane. The optical system sequentially comprises, along the optical axis direction, a front (rear) group and a concave-spherical reflector. The front and the rear groups share a common optical element group, which sequentially comprises, along the optical axis direction, a right-angled reflection prism, a first biconvex positive, a first meniscus thick lens, a second meniscus thick lens and a three-piece optical structure. An aperture diaphragm is arranged on the concave-spherical reflector to form a completely symmetrical structure with a -1 amplification rate of the projection optical system. Accordingly, the inventive diffractive-refractive projection optical system can effectively correct aberration and improve imaging quality; and can effectively shorten the total length of the projection optical system and achieve longer working distance.

Description

technical field [0001] The invention relates to a projection optical system, in particular to a catadioptric projection optical system used in related fields such as semiconductor lithography. Background technique [0002] With the development of projection lithography technology, the performance of projection optical system is gradually improved, and can be applied to various fields such as integrated circuit manufacturing. Projection lithography technology has been successfully applied to the field of sub-micron resolution integrated circuit manufacturing. At the same time, in semiconductor packaging technology, projection lithography technology is used to require lower High-yield gold bumps / tin bumps, wafer-level chip-scale packaging (WLCSP) technology and other fields, and for lower-resolution projection objective lens systems, there are continuous demands for improvement and performance improvement. [0003] In order to meet the requirements of the above-mentioned proj...

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Problems solved by technology

[0004] However, the general projection exposure system expects a larger working distance and a shorter total optical length for the projection optical system.

However, in the five embodiments of the optical system given in the patent, the working distance only reaches the range of 7.5mm to 11mm, but the total optical length reaches more than 1150mm to 1200mm

Therefore, in the application of the actual projection optical system, the working distance will impose very strict size restrictions on the design of the workpiece stage, especially the mask stage. For example, for a mask stage using a 0.25 inch (6.35mm) thick reticle, its Dimensional design will be greatly restricted

In addition, the patent does not provide image quality data

An embodiment of this patent adopts an aspheric optical element design, the working distance is only increased to 11.872mm, and the total optical length reaches 1150mm. The introduction of this aspheric optical element will bring great benefits to optical processing, optical inspection, etc. Difficulties

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