高数值孔径投影光刻物镜的光学设计

针对45nm节点投影光刻物镜的应用,开展了工作波长为193nm的深紫外浸没式高数值孔径(NA)投影光刻物镜的研究和研制。设计了数值孔径(NA)为1.30的离轴三反射镜投影光刻物镜和NA为1.35的同轴两反射镜投影光刻物镜,并对两个设计方案的优劣进行对比分析,选择了同轴式结构作为最终的设计方案。分析了系统在不同NA情况下可变光阑与其远心度之间的关系,提出了用双可变曲面光阑的设计方案来优化系统的远心度。实验表明,应用本文设计方案,光刻物镜的波像差小于1nm,畸变小于1nm;新型的可变光阑使系统NA在0.85~1.35变化时的最大远心度由5.83~17.57mrad降低至0.26~3.21mrad。本文提出的设计方案为45nm节点高数值孔径投影光刻物镜的研制提供了有益的理论依据和指导。

Optical design of high-numerical aperture lithographic lenses

For the manufacture of a lithographic lens with a 45 nm node, this paper focuses on the development of high numerical aperture (NA), deep ultraviolet (DUV) immersion lithographic lenses. Firstly, an off-axis three mirror projection lithographic objective with the NA of 1.30 and a coaxial two mirror projection lithographic objective with the NA of 1.35 were designed. Two design methods and results were compared and the latter was chosen to be used final design. Then, the relationship between variable stop aperture and telecentricity under different NAs was analyzed. A scheme of dual variable curved apertures was proposed to reduce the image telecentricity of a lithographic lens. The final results show that both wavefront errors(Root MeanSquare,RMS) and distortion of the lithographic lens are less than 1 nm by using the proposed scheme. The new scheme with dual variable curved apertures makes the maximum telecentricity decreases from 5.83-17.57 mrad to 0.26-3.21 mrad when NA varies from 0.85 to 1.35. This scheme provides an advantageous theoretical guidance and basis for research and development of the lithographic lens with 45 nm node.