照明物镜像差对远场衍射波前质量影响的严格矢量分析

点衍射干涉仪(PDI)中衍射参考球面波的质量受照明物镜像差和小孔的质量、状态的影响。基于矢量衍射理论,分析计算了可见光经过带像差的照明物镜聚焦后经过有限厚度具有实际电导率小孔板的衍射。分析了照明物镜像差对远场衍射波前质量的影响,确定了PDI检测极紫外光刻(EUVL)元件和系统时的最佳直径大小。分析计算得出,当用PDI检测数值孔经(NA)为0.3的系统时,采用直径大小为800nm的小孔较为适宜,其衍射波前均方根(RMS)偏差为6.51×10-5λ,强度均匀性为0.812。当用PDI检测NA为0.3的元件时,采用直径大小为500nm的小孔较为适宜,其衍射波前的RMS非对称偏差为8.40×10-5λ,强度均匀性为0.664。

Rigorous Vector Analysis of the Effect of Illumination Objective Lens Aberration on the Quality of Far-Field Diffracted Wave Front

The quality of the diffracted reference spherical wave in point diffraction interferometer (PDI) depends on the aberrations in the illumination objective lens and the quality and status of the pinhole. The pinhole diffraction of the visible light focused by the aberrated illumination objective lens is calculated based on the vector diffraction theory, the finite thickness and real conductivity of the pinhole are considered. The effect of illumination objective lens aberration on the quality of far-field diffracted wave front is analyzed. The best pinhole diameter of the PDI used to test the extreme ultraviolet lithography (EUVL) system and its element are determined. The calculation and analysis show that, when a system with NA of 0.3 is tested by PDI, the appropriate pinhole diameter is 800 nm, the RMS deviation of the diffracted wave front is 6.51×10-5λ, intensity uniformity is 0.812, when an optical element with NA of 0.3 is tested by PDI, the appropriate pinhole diameter is 500 nm, the RMS deviation of the diffracted wave front is 8.40×10-5λ, intensity uniformity is 0.664.