NA1.35投影光刻光学系统偏振像差的优化

为了实现NA1.35投影光刻光学系统高质量成像,在设计过程中除了控制波像差,还需进一步优化光学系统的偏振像差。利用Jones光瞳和物理光瞳表达了NA1.35投影光刻光学系统的偏振像差,并用二向衰减量与延迟量分析了光学系统偏振像差的大小;根据光线入射到不同光学面上最大入射角度的不同,为每个光学面设计相应的膜系以优化光学系统的偏振像差。相比于采用常规膜系,膜系优化后NA1.35投影光刻光学系统的二向衰减量和延迟量分别减小到了0.021 8、0.057 2 rad,即减小了光学系统的偏振像差。利用Prolith光刻仿真软件,分别对采用常规膜系和优化膜系的NA1.35投影光刻光学系统进行曝光性能仿真,结果显示:膜系优化后光学系统的成像对比度提高了4.4%,证明了NA1.35投影光刻光学系统偏振像差优化方法的有效性。

Optimization of polarization aberration for NA1.35 lithographic projection optical system

In order to obtain high imaging quality of numerical aperture(NA)1.35 lithographic projection optical system, except for controlling the wavefront aberration, the polarization aberration also should be optimized during design process. The polarization aberration of NA1.35 lithographic projection optical system was expressed by the use of Jones pupils and physical pupils, and the magnitude of polarization aberration was analyzed with bi-attenuation and retardation. According to the max incident angles of different optical surfaces, corresponding coatings of each optical surface were designed to optimize polarization aberration of optical system. After optimizing coatings, the diattenuation and retardation of NA1.35 lithographic projection optical system decrease to 0.021 8 and 0.057 2 rad separately compared with regular coatings, it means that the polarization aberration of optical system decreases. Using lithographic simulation software Prolith to simulate the lithography performance with regular coatings and optimized coatings separately, the result shows that the image contrast with optimized coatings increases 4.4%, proving the effectiveness of the method for optimizing polarization aberration of NA1.35 lithographic projection optical system.