摘要
针对光刻机照明系统矩形光场的均匀照明需求,提出了一种基于单排平凸微柱面镜阵列与小长宽比积分棒相结合的匀光单元方案。分析了小长宽比积分棒输入光场的角度分布特性和宽度对照明均匀性的影响。使用单排平凸微柱面镜阵列进行预匀光可以满足积分棒输入光场需求。采用光线方向余弦的分布偏差表征照明均匀性,构造了匀光单元透镜组的均匀性评价函数,并以KrF光刻机匀光单元为对象,利用CODE V软件对平凸微柱面镜和聚光镜组进行了自动优化设计。在LightTools中对该匀光单元进行仿真验证,结果表明,在不同部分相干因子的传统照明模式和环形照明模式下输出光场的积分非均匀性均小于0.43%,优于基于弥散斑均方根评价函数优化设计的对照组结果,对相关工程设计有一定参考意义。
Objective Lithography is currently an essential tool in the production of integrated circuits(ICs) and other micro-and nano-scale elements used widely in the electronics industry.The resolutions of deep-ultraviolet step-and-scan dry lithography machines in the international market range from 57 nm to 350 nm.The illumination system is an important component of the lithography exposure system.The illumination mode is typically adjustable according to the mask pattern,including a full circle,annular rings,or poles,to improve resolution,imaging contrast,and focal depth.During the IC manufacturing process,the exposure field is scanned using a narrower illumination field.Therefore,illumination-integrated nonuniformity is a key factor in determining the resolution and critical dimension uniformity(CDU),which are crucial to the performance of advanced lithography systems.To obtain higher resolutions and better CDU,the exposure dose must be maintained as uniformly as possible in the scanning direction.The illumination uniformity unit is the primary component for obtaining a uniform illumination field.Currently,the homogenizer elements used in lithography illumination systems include diffractive optical elements(DOEs),microlens arrays(MLAs),and integrator rods.The adoption of DOEs is limited to small angles and reduces transmission efficiency owing to typical diffraction losses.MLAs are refractive optical elements(ROEs) suitable for large numerical apertures(NAs) with minimal energy loss and no effect on laser beam polarization.However,MLAs remain expensive and difficult to process,install,and adjust.Although integrator glass rods are simple in structure,easy to process,and inexpensive,their length-to-width ratio becomes extremely large when small NA and sufficient reflections are required,making them unsuitable for space conservation.This research intends to be beneficial in terms of reducing structural complexity and production costs,as well as improving the effectiveness of the illumination uniformity unit? s automatic
作者
王刚
李中梁
袁春晓
张方
Wang Gang;Li Zhongliang;Yuan Chunxiao;Zhang Fang(Laboratory of Information Optics and OptoElectronics Technology,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2023年第13期131-141,共11页
Chinese Journal of Lasers
基金
上海市集成电路科技支撑专项(20501110600)
上海市政府间科技合作计划(20500711300)
中国科学院青年创新促进会资助项目。
关键词
光学设计
光刻
照明系统
匀光单元
照明均匀性
optical design
lithography
illumination system
homogenizer
illumination uniformity
