基于匀光管的极紫外消相干和光强均匀化仿真研究  

Simulation study of decoherence and light intensity uniformization for extreme ultraviolet of uniform light pipe

作　　者：李慧 谭芳蕊 尹皓玉 马钺洋 吴晓斌 Li Hui;Tan Fang-Rui;Yin Hao-Yu;Ma Yue-Yang;Wu Xiao-Bin(R&D Center of Optoelectronic Technology,Institute of Microelectronics of the Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院微电子研究所,光电技术研发中心,北京100029 [2]中国科学院大学,北京100049

出　　处：《物理学报》2024年第11期133-144,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:62071464);中国科学院前瞻战略科技先导项目(A类先导项目)资助的课题。

摘　　要：自由电子激光光源(free electron laser,FEL)可发出波长为13.5 nm的极紫外(extreme ultra-violet,EUV)辐射,在EUV光刻领域能够发挥重要作用.但FEL自身的高相干特性以及类高斯光强轮廓分布特征,会对成像带来不利影响,无法满足EUV光刻领域成像应用需求.本文通过计算模拟的方法,设计了一种匹配FEL应用的、用于EUV波段去相干和光强均匀化的新型匀光管结构.模拟结果显示,针对波长为13.5 nm、直径200μm、发散度20 mrad的FEL-EUV高斯光束,采用新型匀光管结构,与常规匀光管结构相比,在同等长度和内径时,具有更显著的去相干能力和光场均匀化作用.当新型匀光管内径为1 mm、总长度不低于0.6 m、倾斜角度为10 mrad时,高相干光场完全被扰乱,实现低相干光输出.并可获得均匀照明光场,光强分布不均匀性数值从常规圆柱型匀光管的28.38降低至0.97.同时,相应能量传输效率为37.6%,最大传输效率达到44.58%.结果表明,新型匀光管结构能够满足EUV辐射去相干应用需求,同时可提高照明视场光强分布均匀性,在EUV光刻领域及其他成像应用具有很大应用前景.Free electron laser(FEL)is a high-quality laser source with wavelengths ranging from short-wave X-ray to long-wave infrared ray.Extreme ultra-violet(EUV)radiation atλ=13.5 nm emitted by FEL can be used in manufacturing integrated circuit,such as EUV lithography exposure and mask defect inspection.However,the high spatial coherence characteristics and similar Gauss intensity profile distribution of FEL source has a negative effect on imaging,and cannot meet the requirements of imaging applications in EUV lithography.In this work,a newly light pipe for decoherence and intensity uniformity in an EUV spectral range is designed through the simulation calculations.The new light pipe consists of two pairs of tilted elements which are symmetrically distributed in the y-z plane and x-z plane,respectively.In this way,the beam transmission divergence in two dimensions can be widened at the same time,and the disturbance of the ray transmission track and spatial phase distribution is increased,so as to achieve the uniformization of light intensity and the reduction of spatial coherence.The simulation results show that for an EUV Gaussian beam atλ=13.5nm,with a diameter of 200μm,and a divergence of 20 mrad,the newly designed light pipe has more significant decoherence and illumination field uniformity than the conventional light pipe structure.When the new light pipe has an inner diameter of 1mm,a total length of not less than 600 mm,and a tilt angle of 10mrad,a basically uniform illumination field can be obtained,the coherence is completely disordered,and the non-uniformity of light intensity distribution in the illumination field decreases to 0.97 from 28.38 achieved by conventional cylindrical light pipe.At the same time,the light power transmission efficiency is about 37.6%and the maximum transmission efficiency is about 44.58%.The uniformity can be further improved by increasing the number of reflections.When the inner diameter and tilted angle of the light pipe are unchanged,the length of the light pipe increases to 1

关 键 词：极紫外光源 自由电子激光 匀光管 相位 光强均匀性 

分 类 号：TN2[电子电信—物理电子学]