极紫外光源用大口径Mo/Si多层膜厚度控制与热稳定性研究  

Thickness Control and Thermal Stability of Large⁃Diameter Mo/Si Multilayer Films for Extreme Ultraviolet Source

作　　者：刘翔月 张哲[1] 蒋励[1] 宋洪萱 姚殿祥 黄思怡[1] 徐文杰 霍同林[3] 周洪军[3] 齐润泽 黄秋实[1] 张众[1] 王占山[1] Liu Xiangyue;Zhang Zhe;Jiang Li;Song Hongxuan;Yao Dianxiang;Huang Siyi;Xu Wenjie;Huo Tonglin;Zhou Hongjun;Qi Runze;Huang Qiushi;Zhang Zhong;Wang Zhanshan(Institute of Precision Optical Engineering,School of Physical Science and Engineering,Tongji University,Shanghai 200092,China;College of Sciences,Shanghai University,Shanghai 200444,China;National Synchrotron Radiation Laboratory,University of Science and Technology of China,Hefei 230029,Anhui,China)

机构地区：[1]同济大学物理科学与工程学院精密光学工程技术研究所,上海200092 [2]上海大学理学院,上海200444 [3]中国科学技术大学国家同步辐射实验室,安徽合肥230029

出　　处：《中国激光》2024年第7期187-195,共9页Chinese Journal of Lasers

基　　金：国家自然科学基金(12204353,12075170,U2030111)。

摘　　要：Mo/Si多层膜是13.5 nm极紫外波段理想的反射镜膜系,它与极紫外光源的结合使得极紫外光刻成为了目前最先进的制造手段之一。极紫外光源的实际应用对Mo/Si多层膜提出了高反射率、高热稳定性、抗辐照损伤、大口径等诸多要求。针对极紫外光源用Mo/Si多层膜面临的膜厚梯度控制和高温环境问题,利用掩模板辅助法对大口径曲面基底上不同位置处的多层膜膜厚进行修正;选择C作为扩散阻隔层材料,对磁控溅射法制备的Mo/Si、Mo/Si/C和Mo/C/Si/C三种多层膜在300℃高温应用环境下的热稳定性展开了研究。研究结果表明:通过掩模板辅助的方式能够将300 mm口径曲面基底上不同位置处的Mo/Si多层膜膜厚控制在预期厚度的±0.45%以内,基底上不同位置处Mo/Si多层膜的膜层结构和表面粗糙度基本相同;引入C扩散阻隔层后,经过300℃退火,Mo/Si多层膜的反射率损失从9.0%减少为1.8%,说明C的引入能够有效减少高温对多层膜微结构的破坏和对光学性能的影响,提高了多层膜的热稳定性。Objective Mo/Si multilayer films exhibit the highest measured reflectivity in the extreme ultraviolet(EUV)region,and their combination with an EUV light source enables EUV lithography.In practical applications of EUV light sources,Mo/Si multilayer mirrors are always curved and have large diameters.The angle of the incident light constantly changes along the curved surface.To match the multilayer peak reflectivity with the angle of the incident light,the period thickness of the Mo/Si multilayer films must be distributed in a transverse gradient along the surface to ensure high EUV reflectivity.Simultaneously,given that the mirror is close to the light source,the multilayer films must operate in an environment with a high thermal load.Higher temperatures can increase the formation of silicide at the multilayer interface,causing the optical performance to decrease.Therefore,Mo/Si multilayer films for EUV light sources also have high thermal stability requirements.To address these issues,we use a shadow mask to correct the periodic thicknesses of the multilayer films at different positions on a curved substrate with a diameter of 300 mm.Carbon is selected as the diffusion barrier material to investigate the influence of C-barrier layer on the thermal stability of Mo/Si multilayer.Methods In this study,two sets of Mo/Si multilayer films are deposited via direct current(DC)magnetron sputtering onto superpolished silicon wafers,and the thickness control and thermal stability of the Mo/Si multilayer films are investigated separately.For the study of thickness control,the target period thickness is from 6.96 nm to 7.31 nm,and the ratio of Mo layer thickness to period thickness is approximately 0.40.As the multilayer thickness on a large curved substrate cannot be measured directly,we prepare a substituted substrate to estimate the multilayer thickness at selected points on the surface.The shadow mask technique is used to adjust the periodic thickness of the multilayer films at different positions on the entire mirror.C is

关 键 词：激光光学 极紫外光源 MO/SI多层膜 磁控溅射 膜厚控制 热稳定性 

分 类 号：O434[机械工程—光学工程]