基于Ronchi剪切干涉的投影物镜数值孔径测量方法  

Measurement Method for Numerical Aperture of Projection Lens Based on Ronchi Lateral Shearing Interferometry

作　　者：卢云君[1,2] 李中梁 唐锋[1] 王向朝 Lu Yunjun;Li Zhongliang;Tang Feng;Wang Xiangzhao(Laboratory of Information Optics and OptoElectronic Technology,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院上海光学精密机械研究所信息光学与光电技术实验室,上海201800 [2]中国科学院大学材料与光电研究中心,北京100049

出　　处：《中国激光》2023年第13期94-102,共9页Chinese Journal of Lasers

基　　金：国家科技重大专项(2017ZX02101006);国家自然科学基金(61971406,81927801);中国科学院青年创新促进会项目。

摘　　要：数值孔径(NA)作为投影物镜的基本参数,决定了投影物镜的成像分辨率。在利用双光栅Ronchi剪切干涉仪测量投影物镜波像差时,NA也是实现波像差高精度检测的一项基本参数。提出了一种基于Ronchi剪切干涉像面光栅轴向离焦的投影物镜NA测量方法,理论推导了像面光栅离焦时空间光程差的数学表达式,通过测量轴向两个不同位置处的剪切波前并提取倾斜项系数,利用两个轴向位置的距离以及倾斜项系数的差值计算得到投影物镜NA值。在此基础上,开展了仿真分析和实验,以NA设计值为0.3的投影物镜为测量对象,实验测得NA为0.292,测量误差小于0.004。同时开展了几何光学测量方法的对比实验,进一步验证了所提方法的有效性。该方法利用波像差检测装置测得的剪切波前实现投影物镜NA的在线测量,不需要使用额外的装置或器件。Objective The wavefront aberration and the numerical aperture(NA) of projection lens directly determine the critical dimension and resolution in lithography.Hence,high-accuracy wavefront and NA measurement is crucial in lithography systems.With the advantages of a common optical path,null testing,and no need for extra ideal reference,double-grating Ronchi lateral shearing interferometry(LSI) has great potential for high-accuracy and high-dynamic-range wavefront measurement,which is suitable for online wavefront aberration measurement of the projection lens in lithography.In Ronchi LSI,NA is also a basic parameter for wavefront measurement.Traditional method of NA measurement needs to measure the focal length and the exit pupil diameter.Although there are many ways to measure the focal length,the diameter of exit pupil cannot be measured,unless the aperture of the system is that of the last element.The method which uses the commercial Abbe apertometer(Zeiss) is relatively mature,however,this method requires manual adjustment of the vernier and surveyors have to observe at the exit pupil plane,which increases the complexity of the measurement process.In the present study,we report a new method of NA measurement in the double-grating Ronchi LSI system.With theoretical derivation of the geometric optical path difference introduced in the shearing wavefront,by measuring the shearing wavefront and calculating the tilt coefficient(the coefficient of Zernike Z2 in X-direction shearing wavefront or Z3 in Y-direction shearing wavefront) at two different axial positions,NA is calculated by using the distance between the two axial positions and the differential value of the tilt coefficients.This method can be integrated easily into the current double-grating Ronchi LSI system,which can achieve the online measurement of the NA and wavefront simultaneously.Methods The image-plane grating is moved along the axial direction(Z direction) in the study.Taking the X-direction shearing interferogram for example.The projection lens u

关 键 词：测量 数值孔径测量 投影物镜 Ronchi剪切干涉 剪切波前 光程差 

分 类 号：O436[机械工程—光学工程]