A free-form catadioptric lithography projection objective lens

Abstract

The invention provides a free-form surface turn-back type lithographic projection lens, and belongs to the technical field of high-resolution projection lithography lenses. The free-form surface turn-back type lithographic projection lens comprises a first lens group G1, a second reflector group G2 and a third lens group G3, wherein the first lens group G1 is of a double-gaussian structure, so that a mask (object plane) is imaged to a first middle image while a telecentric object space is ensured; the second reflector group G2 is of a reflecting structure, so that the first middle image is imaged to a second middle image; the third lens group G3 is a convergent lens group, so that the second middle image is imaged to a silicon wafer (image plane), high numerical aperture of an image space is achieved and 1 / 4 object image zooming ratio of a system is finally achieved. 23 optical elements are used by the system in all, wherein free-form surfaces are adopted by 4 surfaces and the numerical aperture reaches 1.2; through adjustment of various free-form surface parameters, the projection lens has excellent imaging quality and a compact structure; materials are saved, the comprehensive monochromatic wave aberration mean square root (RMS) is smaller than 0.005lamda and the full-field aberration is smaller than 1nm.

Description

technical field [0001] The invention relates to a free-form reflective lithography projection objective lens, which can be used in a scanning-stepping deep ultraviolet lithography system, and belongs to the technical field of optical design. Background technique [0002] Lithography is an integrated circuit manufacturing technology, optical lithography is the mainstream technology, and the lithography projection objective lens is the core component of the projection exposure device. The IC pattern on the mask is projected onto the rubber-coated silicon wafer through the lithography projection objective lens. [0003] Due to the continuous improvement of science and technology, various semiconductor chips are widely used in civil fields such as aerospace, military and computers, so the requirements for lithography technology are getting higher and higher. Foreign immersion lithography machines have been industrialized. Japan’s Nikon, Canon, Netherlands ASML, and Germany’s Ca...

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Problems solved by technology

[0005] The existing U.S. Patent US8643824B2 reports the design of the free-form surface deep ultraviolet lithography objective lens, which uses 6 free-form surface mirrors and 6 spherical refracting elements to make the numerical aperture of the image side reach 0.8, and the wave aberration is 80mλ. Although the components used in the system The number is small, but its numerical aperture is small, the resolution is low, and it does not meet the requirements of high imaging performance

[0006] The thirty-sixth structure of the existing US patent US7869122B2 has an image square numerical aperture of 1.2, which can meet the design requirements of high resolution, but the structure contains 25 optical elements, the total thickness of the glass material is 659mm, and the total length of the system is 1253mm , the number of components is large, which affects the transmittance of the system, and the volume is large, which is not conducive to mechanical adjustment

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