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为实现λ/100峰谷值(PV)的光刻投影物镜面形检测精度要求,深入分析了自重变形对大口径超高精度Fizeau干涉仪的光学性能产生的影响。设计的球面标准具结构,其系统波像差达到λ/1000(PV)、像方数值孔径(NA)值为0.36,用于口径超过300 mm的球面镜面形检测。使用Patran/Nastran软件通过有限元方法(FEM)对标准具镜组中一块镜子在胶结辅助支撑和压圈切向支撑两种支撑方式下的自重变形进行分析的基础上,得出在假定载荷作用下各光学元件表面的变形量及刚体位移量。利用泽尼克多项式将变形量大小进行拟合,得到镜子的波像差大小,完成光机转换,分析得到适合的支撑方式。将此支撑方式运用到整个系统,实现了在自重变形下系统的波像差大小优于λ/100(PV)水平。结果证明采用这种支撑方式,可以满足超高精度检测要求,为合理的干涉仪设计提供了数据依据、为提高系统精度奠定了基础。
In order to realize the precision of lithography projection objective detection of λ / 100 peak-to-valley (PV), the influence of self-weight deformation on the optical performance of large-diameter ultra-high precision Fizeau interferometer was analyzed. The designed spherical etalon has a system wavefront aberration of λ / 1000 (PV) and an image side numerical aperture (NA) of 0.36 for spherical mirror detection with a diameter of more than 300 mm. Using Patran / Nastran software, the finite element method (FEM) was used to analyze the self-weight deformation of a mirror in the standard mirror set under the two kinds of supporting modes of cemented support and compression ring tangential support. Under each optical element surface deformation and rigid body displacement. By using the Zernike polynomial, the size of the deformation is fitted to obtain the wave aberration of the mirror, the conversion of the optical machine is completed, and the suitable supporting mode is obtained. Applying this supporting method to the whole system, the wave aberration of the system is better than λ / 100 (PV) under the self-weight deformation. The results show that using this kind of support method can meet the requirements of ultra-high precision detection, provide data basis for reasonable interferometer design, and lay a foundation for improving system accuracy.