An off-axis unobstructed extreme ultraviolet projection lithography objective

Abstract

The invention discloses an off-axis unblocked extreme ultraviolet lithography objective lens. A fifth reflector and a sixth reflector are rotated and slanted, a middle image can be imaged on an image face of the extreme ultraviolet lithography objective lens through the fifth reflector and sixth reflector in an unblocked mode, and the problem of edge view field optical MFA and resolving power reduction caused by light path blocking exists between the upper edge of the fifth reflector and the lower edge of the sixth reflector after the system NA is increased can be solved. Design parameters of six lenses are improved, the image space NA of the extreme ultraviolet lithography objective lens achieves 0.4, and the lithography resolving power is accordingly improved. The width of the image space scanning direction view field achieves 1.5 mm, and the productivity of silicon wafers is guaranteed. Parameters of non-rotational symmetry free hook faces on the six lenses are improved, the obtained projective lithography objective lens has the excellent imaging quality, all values of view field wave aberration RMSs are smaller than 0.0442 lambda, and the full view field change distortion is smaller than 1.85 nm.

Description

technical field [0001] The invention relates to an off-axis unobstructed extreme ultraviolet projection lithography objective lens, which can be used in a scanning-step extreme ultraviolet lithography system and belongs to the technical field of optical design. Background technique [0002] As the most promising next-generation lithography technology, extreme ultraviolet lithography can meet the industrialization requirements of semiconductor manufacturing at 16nm and higher technology nodes. Extreme ultraviolet lithography uses a light source with a wavelength of 11-15nm for illumination. Since almost all optical materials have strong absorption in this wavelength band, the extreme ultraviolet lithography system uses reflective optical components coated with reflective films. As the core component of the extreme ultraviolet lithography system, the extreme ultraviolet projection lithography objective lens has the design requirements of high resolution, high image quality and...

AI Technical Summary

Problems solved by technology

However, the imaging distortion of this system reaches 12nm, and the imaging accuracy cannot be achieved.

[0007] The existing off-axis unobstructed 6-mirror design is the third structure in US2012 / 0069314A1. This structure has very good imaging performance, but the total length of the system reaches 1849mm, which is not conducive to processing and manufacturing, and the numerical aperture is 0.38. Improving the resolution of the lithography system is not effective

[0008] The existing unobstructed 6 mirrors design the structure in Chinese patent CN102608737. This structure has better imaging performance, but the numerical aperture is only 0.25, which cannot meet the extreme ultraviolet high resolution imaging requirements.

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