Protective layer of oxides and nitrides on the surface of extreme ultraviolet multilayers
-
摘要: 极紫外（EUV）反射镜在高能、高功率极紫外光辐照的过程中，其表面易形成碳沉积和氧化，从而影响其反射率，进而缩短其使用寿命。针对这一问题，分别实验研究了在极紫外多层膜表面镀制氮化物和氧化物保护层的制备工艺，并进行了表征。在制备过程中，基于直流反应磁控溅射技术，研究了工艺气体流量与溅射电压之间的“双曲线”关系，以此优化控制反应气体量，进而降低反应溅射过程中反应气体对Mo/Si多层膜的影响。基于这一方法，分别在Mo/Si多层膜表面镀制TiN、ZrN和TiO2保护层，应用掠入射X射线反射（GIXR）、X射线光电子能谱（XPS）和透射电子显微成像（TEM）对其进行了表征，并通过对比分析，验证了氮化物保护层具有一定的性能优势。Abstract: In the process of high energy and high power extreme ultraviolet (EUV) irradiation, carbon deposition and surface oxidation are easy to form on the surface of the EUV mirror, which will affect its reflectivity and shorten its service life. To solve this problem, technology of nitride and oxide capping coating on the surface of extreme ultraviolet multilayer film was studied experimentally and characterized. In the preparation process, based on DC reactive magnetron sputtering coating technology, the “hyperbola” relationship between process gas flow and sputtering voltage was studied, to optimize the control of the amount of reactive gas, and then reduce the influence of reactive gas on Mo/Si multilayer films during reactive sputtering. Based on this method, TiN, ZrN and TiO2 capping layer were plated on the surface of Mo/Si multilayer films and were characterized by grazing incident X-ray reflection (GIXR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It is proved that the nitride capping layer has certain performance advantages.
-
随着科学技术的发展，核技术具有零碳排放、能源独立、安全等诸多优势，在人类社会中的地位越来越重要。然而，核辐射事故却为核技术发展迅速蒙上了一层阴影。1986年，苏联切尔诺贝利核电站发生了迄今为止人类历史上最严重的核辐射事故[1]。2011年，日本东北海岸发生了里氏9.0级的强烈地震和海啸，造成了福岛第一核电站的1～3号机组反应堆熔毁[2]。由于反应堆内部高温和高辐射等极端环境，人类无法直接进入进行勘察和处置工作，因此在福岛事故中使用了多种类型和功能的机器人。光纤激光器具有高功率、高光束质量，光束可以远距离柔性传输等优点，可以用于无人区开展激光切割救援等工作[3]。比如Shin等人研究了用10 kW光纤激光器拆除核设施的150 mm厚的厚钢板和大型管道的切割性能[4]。当然，光纤激光器在辐射环境中也会受到影响[5]，高能射线会导致增益光纤产生色心等各类缺陷，这些缺陷引起的额外光吸收增加了传输损耗，降低了光纤激光器性能。
课题组基于光纤激光器存在的自漂白效应，利用60CO辐照源探索不同辐照剂量率下的光纤激光器暗化与自漂白的平衡关系。实验先采用低功率光纤振荡器进行不同辐照剂量率下激光器输出功率演化和去辐照后自漂白研究。使用的光纤激光振荡器实验结构如图1所示，谐振腔由常规商业掺镱光纤（YDF）、高反射光纤光栅（HR-FBG）、低反射光纤光栅（OC-FBG）构成，中心波长为976 nm的泵浦源（LDs）通过前向（2+1）×1泵浦信号合束器（FPSC）注入到谐振腔中，激光经过包层光滤除器（CLS）后由光纤端帽（QBH）扩束输出。
首先，利用较高辐照剂量率研究在去辐照后的自漂白效应，结果如图2（a）所示。图2（a）的(I)为未辐照阶段，持续时间为680 s，由于水冷机周期性制冷使得功率计温度周期变化导致测试激光功率也存在周期变化，激光器功率起伏为1.44%；需要注意的是，这个是主要功率测量误差导致，并不是激光器本身功率起伏。图2（a）中(II)为辐照阶段，在总辐照时间298 s内，辐照总剂量为14 900 rad，激光器输出功率从150 W下降至105 W。图2（a）的(III)为去辐照后的自漂白阶段，在光纤激光器的泵浦光子与热效应的共同作用下，激光器输出功率从118 W恢复di至145 W，与初始功率相差仅5 W，表明自漂白效应可以较为有效地恢复由于辐照导致的激光功率下降。
图 2 光纤激光器在辐照环境下的输出特性Figure 2. Output characteristics of the optical fiber laser in an irradiated environment然后，为了探索不同剂量率的自漂白与在线辐照相互作用是否可以达到平衡，开展了不同剂量率的对比研究，结果如图2（b）所示。图2（b）中，总辐照剂量为2 400 rad，红色、蓝色曲线分别对应辐照剂量率为50 rad/s、1 rad/s时激光器归一化输出功率演化情况；在辐照剂量率为50 rad/s时，激光输出功率下降了3%；在辐照剂量率1 rad/s时，功率起伏1.22%，考虑到这里的周期性起伏主要由于水冷机周期性制冷导致，可以认为在低辐照剂量率下，光纤激光器自漂白导致的功率提升与辐照导致的功率下降基本达到平衡。
进一步地，基于图2（b）的实验结果，我们验证了1 kW级光纤激光器中自漂白与辐照平衡的实验现象。在辐照剂量率为0.1 rad/s时，激光器输出激光功率曲线演化如图2（c）所示。从实测功率曲线来看，在总辐照剂量为190 rad的整个辐照过程中，光纤激光器的输出功率都稳定在1 050 W以上，即使考虑前述由于水冷机导致的功率变化，激光器的功率起伏在1.79%以内。如果不考虑水冷机周期性制冷影响，激光器的功率起伏在0.66%以内。
实验首次验证了在一定辐照剂量率下，光纤激光器自漂白效应导致的激光功率提升可以平衡辐照效应导致的功率下降，为相关场景应用的光纤激光器设计提供了有效支撑。后续，我们将继续深入相关研究，探索不同类别、不同结构激光器辐照与自漂白平衡的机理、阈值和可能的应用。
-
图 1 Mo/Si多层膜GIXR测试及拟合结果
Figure 1. GIXR test and fitting results of the Mo/Si multilayer film
图 5 含有TiN保护层的多层膜GIXR测试及其拟合结果
Figure 5. GIXR test and fitting results of multilayer film with TiN capping layer
图 7 含有TiN保护层的Mo/Si多层膜TEM测试结果
Figure 7. TEM analysis results of Mo/Si multilayer film with TiN capping layer
图 8 含ZrN保护层的Mo/Si多层膜GIXR测试及其拟合结果
Figure 8. GIXR test and fitting results of multilayer film with ZrN capping layer
图 10 含有ZrN保护层的Mo/Si多层膜TEM测试结果
Figure 10. TEM analysis results of Mo/Si multilayer film with ZrN capping layer
图 11 含有TiO2保护层的Mo/Si多层膜GIXR及其拟合结果
Figure 11. GIXR test and fitting results of multilayer film with TiO2 capping layer
图 13 含有TiO2保护层的Mo/Si多层膜TEM测试结果
Figure 13. TEM analysis results of Mo/Si multilayer film with TiO2 capping layer
表 1 TiNX薄膜成分表
Table 1. TiNX film composition table
material mass fraction of Ti/% mass fraction of N/% mass fraction of O/% TiNX 46.0 45.6 8.4 
下载: 导出CSV
表 2 ZrNY薄膜成分表
Table 2. ZrNY film composition table
material mass fraction of Zr/% mass fraction of N/% mass fraction of O/% ZrNY 46.9 45.7 7.4
下载: 导出CSV
表 3 TiOZ薄膜成分表
Table 3. TiOZfilm composition table
material mass fraction of Ti/% mass fraction of O/% TiOZ 33.5 66.5
下载: 导出CSV
-
[1] Madey T E, Faradzhev N S, Yakshinskiy B V, et al. Surface phenomena related to mirror degradation in extreme ultraviolet (EUV) lithography[J]. Applied Surface Science, 2006, 253(4): 1691-1708. doi: 10.1016/j.apsusc.2006.04.065 [2] 李超逸, 陶保全, 郭祥帅, 等. 极紫外多层膜技术的研究进展[J]. 量子光学学报, 2020, 26(4):397-408Li Chaoyi, Tao Baoquan, Guo Xiangshuai, et al. Research progress on extreme ultraviolet multilayer techniques[J]. Journal of Quantum Optics, 2020, 26(4): 397-408 [3] Yulin S, Benoit N, Feigl T, et al. Mo/Si multilayers with enhanced TiO2- and RuO2-capping layers[C]//Proceedings of the SPIE 6921, Emerging Lithographic Technologies XII. 2008: 692118. [4] Hollenshead J T, Klebanoff L E, Delgado G. Predicting radiation-induced carbon contamination of EUV optics[J]. Journal of Vacuum Science & Technology B, 2019, 37: 021602. [5] Motai K, Oizumi H, Miyagaki S, et al. Cleaning technology for EUV multilayer mirror using atomic hydrogen generated with hot wire[J]. Thin Solid Films, 2008, 516(5): 839-843. doi: 10.1016/j.tsf.2007.06.182 [6] 王珣, 金春水, 匡尚奇, 等. 极紫外光辐照下表面碳沉积污染的计算模型[J]. 光学学报, 2014, 34:0531001 doi: 10.3788/AOS201434.0531001Wang Xun, Jin Chunshui, Kuang Shangqi, et al. Simulation model of surface carbon deposition contamination under extreme ultraviolet radiation[J]. Acta Optica Sinica, 2014, 34: 0531001 doi: 10.3788/AOS201434.0531001 [7] Mizutani U, Yamaguchi T, Ikuta H, et al. Fabrication of Mo/Si multilayer mirrors for extreme ultraviolet lithography by means of superconducting bulk magnet magnetron sputtering[J]. Physica C: Superconductivity, 2008, 468(15/20): 1456-1460. [8] Zheng Yi, Sanche L. Effective and absolute cross sections for low-energy (1-30 eV) electron interactions with condensed biomolecules[J]. Applied Physics Reviews, 2018, 5: 021302. [9] Pelizzo M G, Suman M, Monaco G, et al. High performance EUV multilayer structures insensitive to capping layer optical parameters[J]. Optics Express, 2008, 16(19): 15228-15237. [10] Seo H S, Park J, Lee S Y, et al. Properties of EUVL masks as a function of capping layer and absorber stack structures[C]//Proceedings of the SPIE 6517, Emerging Lithographic Technologies XI. 2007: 65171G. [11] Bajt S, Chapman H N, Nguyen N, et al. Design and performance of capping layers for extreme-ultraviolet multilayer mirrors[J]. Applied Optics, 2003, 42(28): 5750-5758. doi: 10.1364/AO.42.005750 [12] Nesládek P, Schmidt J, Krome T. EUV capping layer integrity[C]//Proceedings of the SPIE 10807, Photomask Japan 2018: XXV Symposium on Photomask and Next-Generation Lithography Mask Technology. 2018: 108070E. [13] 王洪昌, 王占山, 李佛生, 等. 帽层对极紫外多层膜反射特性影响分析[J]. 物理学报, 2004, 53(7):2368-2372 doi: 10.3321/j.issn:1000-3290.2004.07.065Wang Hongchang, Wang Zhanshan, Li Fosheng, et al. Analysis of the reflective performance of EUV multilayer under the influence of capping layer[J]. Acta Physica Sinica, 2004, 53(7): 2368-2372 doi: 10.3321/j.issn:1000-3290.2004.07.065 [14] 徐达, 朱京涛, 张众, 等. Mo/Si多层膜表面保护层设计[J]. 光子学报, 2009, 38(1):160-164Xu Da, Zhu Jingtao, Zhang Zhong, et al. Design of capping layers on Mo/Si multilayer[J]. Acta Photonica Sinica, 2009, 38(1): 160-164 [15] Kim T G, Lee S Y, Kim C Y, et al. Characterization of Ru layer for capping/buffer application in EUVL mask[J]. Microelectronic Engineering, 2006, 83(4/9): 688-691. [16] 王珣. 极紫外光学薄膜元件表面抗污染保护层及相关技术研究[D]. 长春: 中国科学院研究生院(长春光学精密机械与物理研究所), 2015Wang Xun. Study on surface anti-contamination capping layer of the EUV optical elements and related technologies[D]. Changchun: Graduate School of Chinese Academy of Sciences (Changchun Institute of Optics, Fine Mechanics and Physics), 2015 [17] Nishiyama I, Oizumi H, Motai K, et al. Reduction of oxide layer on Ru surface by atomic-hydrogen treatment[J]. Journal of Vacuum Science & Technology B, 2005, 23(6): 3129-3131. [18] 周洪军, 钟鹏飞, 霍同林, 等. 同步辐射活化氧清洗碳污染的研究[J]. 光学学报, 2010, 30(3):907-910 doi: 10.3788/AOS20103003.0907Zhou Hongjun, Zhong Pengfei, Huo Tonglin, et al. Cleaning of carbon contamination on Si wafer with activated oxygen by synchrotron radiation[J]. Acta Optica Sinica, 2010, 30(3): 907-910 doi: 10.3788/AOS20103003.0907 [19] 匡尚奇, 李硕, 杨海贵, 等. 极紫外宽带多层膜反射镜离散化膜系的设计与制备[J]. 光学 精密工程, 2018, 26(10):2395-2406 doi: 10.3788/OPE.20182610.2395Kuang Shangqi, Li Shuo, Yang Haigui, et al. Design and fabrication of EUV broadband multilayer mirrors with discrete thicknesses[J]. Optics and Precision Engineering, 2018, 26(10): 2395-2406 doi: 10.3788/OPE.20182610.2395 [20] 祝文秀, 金春水, 匡尚奇, 等. 提高极紫外光谱纯度的多层膜设计及制备[J]. 光学学报, 2012, 32:1031002Zhu Wenxiu, Jin Chunshui, Kuang Shangqi, et al. Design and fabrication of the multilayer film of enhancing spectral-purity in extreme ultraviolet[J]. Acta Optica Sinica, 2012, 32: 1031002 [21] 祝国龙, 冯仕猛, 邵建达, 等. 制备超薄多层膜的自动转速控厚法[J]. 中国激光, 2001, A28(11):1027-1031 doi: 10.3321/j.issn:0258-7025.2001.11.019Zhu Guolong, Feng Shimeng, Shao Jianda, et al. Automatically rotation-speed-controlled layer thickness of ultrathin multilayer reflectors[J]. Chinese Journal of Lasers, 2001, A28(11): 1027-1031 doi: 10.3321/j.issn:0258-7025.2001.11.019 -
下载:
点击查看大图
计量
- 文章访问数: 242
- HTML全文浏览量: 94
- PDF下载量: 30
- 被引次数: 0
