A Pure Refractive Dry Projection Optical System with Large Numerical Aperture

Abstract

The invention relates to a pure reflecting dry type projection optical system with a large numerical aperture. The pure reflecting dry type projection optical system is large in numerical aperture which achieves 0.93. The pure reflecting dry type projection optical system is provided with plate glass; the plate glass which is arranged close to an object side and an image side plays a role in protecting glass. Five lens groups can be sequentially divided from an object surface to an image surface, wherein the lens group which is in a waist shape is located in the third lens group, provided with negative power and benefited to help the system to correct the field curvature. The pure reflecting dry type projection optical system has the advantages of being high in numerical aperture, small in aberration and compact in structure, effectively reducing manufacturing costs and reducing lens machining, detection and adjustment difficulties.

Description

technical field [0001] The invention relates to a projection optical system working on predetermined wavelength ultraviolet light, in particular to a pure refraction dry type projection optical system with large numerical aperture. Background technique [0002] Photolithography is a very important process in the semiconductor manufacturing process. For decades, projection optical systems have been used to manufacture semiconductor components and other precision components. The projection optical system is a device used for scanning and exposing silicon wafers in the photolithography process. The pattern on the mask or reticle passes through the projection optical system and is projected onto the surface of the silicon wafer coated with a photosensitive layer at high resolution. The exposure quality of the projection optical system has a great influence on the whole etching process. [0003] In order to expose finer and finer structures below 100nm, on the one hand, use ultr...

AI Technical Summary

Problems solved by technology

The shorter the wavelength, the fewer materials the optical system can use. For the projection optical system used for ultraviolet light below 260nm, the refraction materials that can be used at present are generally only artificial quartz and fluorinated crystals, etc. Materials, the refractive index of these materials are relatively low, therefore, for the design of large numerical aperture optical system, there will be a large Petzval field curvature, which will cause the image plane of the optical system to be seriously curved, and for the exposure For semiconductor silicon wafers, it is very important to obtain a flat field image

In addition, as the numerical aperture increases, the size of the projection optical system in three directions also increases sharply, which brings difficulties to the production and processing of materials.

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