193_nm激光下不同含量...2晶体辐照损伤研究（英文）_王华进.pdf

第 38 卷 第 2 期 无 机 材 料 学 报 Vol.38 No.2 2023 年 2 月 Journal of Inorganic Materials Feb.,2023 Received date:2022-05-27;Revised date:2022-06-04;Published online:2022-08-26 Foundation item:Strategic Priority Program of the Chinese Academy of Sciences(XDA25020313);National Natural Science Foundation of China(61925508);Science and Technology Commission of Shanghai Municipality(20501110300,20511107400);CAS Project for Young Scientists in Basic Research(YSBR-024)Biography:WANG Huajin(1996),male,Master candidate.E-mail: 王华进(1996),男,硕士研究生.E-mail: Corresponding author:KOU Huamin,associate professor.E-mail:;SU Liangbi,professor.E-mail: 寇华敏,高级工程师.E-mail:;苏良碧,研究员.E-mail: Article ID:1000-324X(2023)02-0219-06 DOI:10.15541/jim20220300 Irradiation Damage of CaF2 with Different Yttrium Concentrations under 193 nm Laser WANG Huajin1,2,KOU Huamin2,WANG Yongzhe2,JIANG Dapeng2,ZHANG Bo2,QIAN Xiaobo2,WANG Jingya2,ZHU Linling4,ZENG Aijun4,YANG Qiuhong1,SU Liangbi2,3(1.School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China;2.State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 201899,China;3.Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China;4.Shanghai Institute of Optics and Fine Mechanics,Shanghai 201800,China)Abstract:Radiation resistance of CaF2 crystal is one of the critical properties in the application of deep ultraviolet lithography,but the damage process under 193 nm laser irradiation is still unclear.This paper reports the damage behavior of CaF2 crystals under 193 nm laser irradiation and the key defect factors affecting the damage.Through the 193 nm laser irradiation experiment,it is found that the crystal damage is mainly manifested as the radiation-induced color centers inside the crystal and the radiation-induced damage pits on the surface.Irradiation-induced color centers were analyzed by UV-visible spectrophotometer,and linear fitting was performed between absorption coefficients of different color centers and Y impurity contents.The results show that Y ion has a low-order orbit that overlaps with the F center structure wave function,and hybridizes to form a stable structure.There is a linear relationship between Y ions contents and intrinsic color centers of CaF2 crystals,confirming that Y element is the key impurity ion affecting the formation of color centers.Energy dispersive X-ray spectrometer(EDS)results show that the content of calcium in the damage pits increases and the content of fluorine decreases,which confirms that the diffusion of H centers and the aggregation of F centers lead to irradiation damage.Electron backscatter diffraction(EBSD)results show that surface irradiation damage occurs preferentially at dislocations.Therefore,reducing the impurity content and dislocation density is an important way to improve the anti-irradiation damage performance of calcium fluoride crystals under 193 nm laser.Key words:CaF2 crystal;color center;laser irradiation damage;impurity content;dislocation density CaF2 has high transparency in the range from 130 nm to 9 m and is widely used in deep ultraviolet(DUV)to far infrared(IR)optical components.It is even more irreplaceable in applications in the extreme UV edge.The most demanding application for CaF2 is DUV optical microlithography,where CaF2 is a crucial lens material.Although the transmittance of CaF2 crystal meets the 193 nm lithography requirements,even when the laser energy density is below the damage threshold,they cannot avoid the optical damage caused by cumulative ultraviolet radiation.This behavior is known as the incubation effect1-4.To improve the resistance of CaF2 to DUV laser irradiation,investigating the interaction between the DUV laser and CaF2 and clarifying the mechanism of laser damage is very important.After irradiation with a 193 nm laser,high-quality CaF2 still show coloration effects to some extent.The investigation of these coloration effects,the so-called laser damage,has been studied intensively in recent years5-9.The coloration of fluorite(natural CaF2)was studied widely.Smakula,et al10-12 obtained the coloring effect of calcium fluoride by X-ray,-ray,neutron irra-diation,and electron irradiation respectively.According to Mies theory13-15,the coloration effects were due to 220 无 机 材 料 学 报 第 38 卷 the formation of colloidal particles in the mineral.Besides,Przibram16 showed that many coloration effects could be associated with impurity ions,especially rare-earth ions.Bill and coworkers17-18 extensively studied the coloration of natural fluorite and doped CaF2 with many impurity ions.Alig,et al19-20 believed that the orbital hybridization of impurity ions such as Y,La,Ce,Gd,Tb,and Lu with intrinsic defects resulted in color center absorption.Among the impurity ions,the Y ion was the main impurity element,Y is easily incorporated into CaF2 lattice du