低密度SnO_(2)靶激光等离子体极紫外光及离带热辐射  

Radiation of extreme ultraviolet source and out-of-band from laser-irradiated low-density SnO_(2) target

作　　者：司明奇 温智琳 张齐进 窦银萍[1] 李博超 宋晓伟[1] 谢卓 林景全[1] Si Ming-Qi;Wen Zhi-Lin;Zhang Qi-Jin;Dou Yin-Ping;Li Bo-Chao;Song Xiao-Wei;Xie Zhuo;Lin Jing-Quan(School of Science,Changchun University of Science and Technology,Changchun 130022,China;Chongqing Research Institute,Changchun University of Science and Technology,Chongqing 401120,China)

机构地区：[1]长春理工大学物理学院,长春130022 [2]长春理工大学重庆研究院,重庆401120

出　　处：《物理学报》2023年第6期209-216,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:U22A2070,62005021,62105040,62175018);重庆市自然科学基金(批准号:cstc2021jcyj-msxmX0735);吉林省科技厅项目(批准号:YDZJ202201ZYTS301,YDZJ202102CXJD028,20210402072GH);吉林省教育厅(批准号:JJKH20220721KJ)资助的课题.

摘　　要：极紫外光刻技术是我国当前面临35项“卡脖子”关键核心技术之首.高极紫外光转换效率和低离带热辐射的激光等离子体极紫外光源是极紫外光刻系统的重要组成部分.本文通过采用激光作用固体Sn和低密度SnO_(2)靶对极紫外光源以及其离带热辐射进行研究.实验结果表明,两种形式Sn靶在波长为13.5 nm附近产生了强的极紫外光辐射.由于固体Sn靶等离子体具有较强自吸收效应,在光刻机中心工作波长13.5 nm处的辐射强度处于非光谱峰值位置.而低密度SnO_(2)靶具有较弱的自吸收效应,其所辐射光谱的峰值恰好位于13.5 nm处.相比于固体Sn靶,低密度SnO_(2)靶中处于激发态的Sn离子发生跃迁所产生的伴线减弱,使其在13.5 nm处的光谱效率提升了约20%.另一方面,开展了极紫外光源离带热辐射(400-700 nm)的实验研究,光谱测量结果表明离带热辐射主要是由连续谱所主导,低密度SnO_(2)靶中含有部分低Z元素O(Z=8),导致其所形成的连续谱强度低,同时离带辐射时间短,因而激光作用低密度SnO_(2)靶所产生的离带热辐射弱于固体Sn靶情况.离带热辐射角分布测量结果表明,随着与靶材法线夹角逐渐增加,离带热辐射强度逐渐减弱,且辐射强度与角度满足Acos^(α)θ的关系.The extreme ultraviolet(EUV)lithography technology required for high-end chip manufacturing is the first of 35“bottleneck”key technologies that China is facing currently.The high conversion efficiency EUV source and low out-of-band radiation play a significant role in the application of the EUV lithography system.In this work,the EUV source and out-of-band radiation are studied by using laser irradiated solid Sn target and low-density SnO_(2) target.The result shows that a strong EUV radiation at a wavelength of 13.5 nm is generated when the laser irradiates the two forms of Sn targets.Owing to the self-absorption effect of the solid Sn target plasma,the maximum intensity of the wavelength is not located at the position of 13.5 nm,which is working wavelength of EUV lithography system.However,the peak radiation spectrum is located at the position of 13.5 nm with low-density SnO_(2) target due to its weaker plasma self-absorption effect.In addition,the satellite lines are weaker in low-density SnO_(2) target than in the solid Sn target,so that the spectrum efficiency of the EUV at 13.5 nm(2% bandwidth)is increased by about 20%.On the other hand,the experimental study of the out-of-band radiation is carried out.The out-of-band radiation spectral results show that the out-of-band radiation is mainly dominated by the continuum spectrum.Compared with the solid Sn target,the low-density SnO_(2) target contains a part of the low Z element O(Z=8),resulting in a low-intensity continuum spectrum.In addition,the collision probability of ion-ion and electron-ion both become low when the laser irradiates the low-density SnO_(2) target,resulting in a short out-of-band radiation duration time.Therefore,the out-of-band radiation generated by the laser irradiated on the low-density SnO_(2) target is weak based on the above reasons.The angular distribution of out-of-band radiation measurement results shows that the intensity of out-of-band radiation decreases with the angle increasing.A cosine function Acos^(α)θ can fit the a

关 键 词：低密度靶 极紫外光源 离带热辐射 光谱效率 

分 类 号：O53[理学—等离子体物理] TN23[理学—物理] TN305.7[电子电信—物理电子学]