Research and progress on optical design of exposure system of extreme ultraviolet lithography machine
Design method of EUV lithography projection objective lens composed of six-sided and multi-sided mirrors with uniform magnification.
*Research in this area date back to 2003.
In 2003, Li Yanqiu [ 66 ] based on the EUV lithography projection objective lens structure, profiling designed an EUV lithography projection objective lens with NA of 0.25 and a large field of view composed of six mirrors. In 2004, he proposed an optimization method for the design of an objective lens composed of six-sided mirrors with an NA of 0.25. In the field of view of 26 mm×1 mm, the wave aberration is less than 0.4 nm, the distortion is less than 3.77 nm, and the resolution can reach 50 nm [ 67 ] .
2) Paraxial search method
In 2003, Bal et al [ 68 - 69 ] proposed a paraxial search method to search for the possible structural solution space of the EUV lithography projection objective lens composed of polygonal mirrors. Based on the principle of matrix optics, this method reduces the number of structural variables of the system by introducing constraints, and performs an exhaustive search on the remaining structural variables. Finally, paraxial ray tracing is used to determine the occlusion, and the unoccluded objective lens structure is screened out. In 2009, Yang Xiong et al.
The most recent efforts.
In 2020, Wu et al. [ 87 ] , Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences proposed a grouping design method based on actual ray tracing combined with initial structural parameters and aberration balance. This method establishes the relationship between the initial structural parameters and the primary aberration, and screens the initial structure of the primary aberration balance by simulating the particle swarm annealing algorithm, and designs and completes a set of EUV lithography projection objectives with an off-axis NA of 0.33. The wave aberration of the objective lens is less than 0.19 nm and the distortion is less than 1 nm in the arc-shaped field of view of 26 mm×2 mm.
In 2022, Li Yanqiu and Yan Xu of Beijing Institute of Technology [ 88 ] proposed a grouping design method based on two-way real ray tracing. The method realizes the calculation of the initial structure of the aspherical EUV lithography objective lens through real ray tracing at the ideal conjugate field point in the forward optical path and the reverse optical path. Through this method, the extreme ultraviolet lithography objective lens system with distortion less than 0.25 nm, wave aberration less than 0.2 nm, and NA of 0.33 in a 26 mm×2 mm arc field of view was designed.
In 2022, Huazhong University of Science and Technology Tan et al. [ 89 ] proposed a method based on Seidel's aberration theory to solve the spherical initial structural parameters of the off-axis EUV lithography projection system composed of six-sided mirrors, so as to design the method. In this method, different initial structures are obtained by performing ray tracing on the initial structure, expressing primary aberrations with structural parameters, and setting different initial conditions. Through this method, two sets of EUV lithography projection objective lens system with NA of 0.25 were designed and completed. The wave aberration of the objective lens in the field of view of 26 mm×1.5 mm is less than 0.53 nm and 0.58 nm, and the distortion is less than 1.2 nm and 0.8 nm respectively.
Design method of high NA variable magnification EUV lithography projection objective lens system.
In 2022, Li Yanqiu and Yan Xu from Beijing Institute of Technology [ 91 ] proposed a large off-axis, variable magnification extreme ultraviolet lithography objective lens grouping design to solve the problem that the diameter of the last mirror of the EUV lithography objective lens with an NA of 0.55 is too large method. This method innovatively designs the objective lens structure, and designs a large off-axis variable magnification EUV objective lens structure, which realizes that the light emitted by the illumination system and reflected by the mask is oriented to a reasonable position, and the objective lens system and the illumination system are separated from each other. No optical path obstruction occurs, and a large off-axis, variable magnification EUV objective lens with excellent structure and performance is obtained. This method designs a large off-axis, variable magnification EUV lithography projection objective with NA of 0.55. The objective lens has a wave aberration of less than 1.02 nm and a distortion of less than 0.12 nm in a field of view of 26 mm×0.5 mm
In 2021, Yue et al. [ 92 ] of the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences proposed a design method for an off-axis reflective variable magnification objective lens system based on vector aberration theory. According to the principle of spatial ray tracing and grouping design, the method establishes the evaluation function related to the structural parameters and optical performance of the variable magnification objective lens, and selects the appropriate initial structure of the objective lens system by simulating the particle swarm annealing algorithm. Using this method, a set of variable magnification EUV lithography projection objective lens with NA of 0.55 was designed. The objective lens has a wave aberration of less than 0.42 nm and distortion less than 2 nm in a field of view of 26 mm×0.5 mm
Extreme ultraviolet lithography illumination system and its design method
In 2017, Li Yanqiu and Jiang Jiahua from Beijing Institute of Technology [ 115-116
established a design method for the relay mirror group of EUV lithography illumination system based on matrix optics. According to the relationship between the imaging characteristic requirements of the relay mirror group and its structural parameters, this method can directly obtain a variety of relay mirror group structures that meet the predetermined imaging characteristic requirements, and effectively improve the design efficiency of the lighting system. The EUV designed by this method The illumination system is well matched to a zoom objective system with an NA of 0.5 such asFigure 15shown.
In 2018, Li Yanqiu and Jiang Jiahua from Beijing Institute of Technology [ 114 ] proposed an automatic optimization method for double-row compound eye matching and alignment relationship. Algorithm to solve the best alignment matching relationship of the double row of compound eyes, and the inclination angle of the compound eye micro-mirror at this time.
In 2022, Li Yanqiu and Yan Xu of Beijing Institute of Technology [ 117 ] used the theory and method of matrix optics to propose a free-form surface relay mirror group design method for extreme ultraviolet lithography illumination system. This method uses a variable magnification relay lens group to magnify the secondary light source with a circular outer envelope at different magnifications, thereby obtaining the required elliptical light source, and using this method to design a set with more reasonable structure and high performance. A better illumination system that matches the zoom objective system with NA of 0.55
