Optical Design of Fourier Transform Lens for Measurement of Illumination Pupil of Lithography Tools

浸液光刻投影物镜的数值孔径目前已经达到1.35,这对与之匹配的照明系统光瞳测量提出了十分苛刻的需求,为此设计了一种用于照明光瞳测量的傅里叶变换物镜。分析了傅里叶变换物镜应该满足的畸变要求,并针对照明光瞳测量实际需求分析了傅里叶变换物镜的正弦条件偏离的阈值,采用对不同视场角预留不同负畸变值的方法,实现了一种傅里叶变换物镜光学设计,采用5块透镜、1种光学材料,满足照明光瞳测量对正弦条件偏离阈值的要求,成像质量接近衍射极限,并对傅里叶变换物镜逆向光路也进行了分析计算。通过傅里叶变换物镜光学设计的具体实例,证实了通过对不同视场角预留不同负畸变值设计方法的有效性,利用该方法可以获得满足实际照明光瞳测量要求的傅里叶变换物镜。Numerical aperture (NA) of the projection objectives of the immersion microlithographic projection exposure machines has reached 1.35 and the measurements of the illumination pupil should meet very stringent requirements. A Fourier transform lens is designed and used for the measurement of the illumination pupil of the immersion microlithographic projection exposure machines. It is analyzed that the distortion of the Fourier transform lens should be negative, and the threshold of the deviation from the sine condition (DSC) of the Fourier transform lens is also analyzed on condition of the actual requirement of the illumination pupil measurement. The design method is that the different negative distortions are set on the different field of view (FOV) positions. We has worked out a Fourier transform lens with five elements and one kind of optical material and it meets the requirements of the DSC, wave front error, modulcotion transfer function (MTF) and distortion for the illumination pupil measurements of the immersion microlithographic projection exposure machines. It is also analyzed when the Fourier transform lens is used at inverse direction. It is confirmed that the design method that the different negative distortions are set on the different FOV positions of the Fourier transform lens is valid