光源空间相干性对深紫外光刻照明均匀性的影响  

Influence of Spatial Coherence of Light Source on Uniformity of Deep Ultraviolet Lithography Illumination

作　　者：宋子健 龚爽 步扬[2] 魏爽 Song Zijian;Gong Shuang;Bu Yang;Wei Shuang(School of Microelectronics,Shanghai University,Shanghai 200444,China;Laboratory of Information Optics and Opto-Electronic Technology,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Zhangjiang Laboratory,Shanghai 201210,China)

机构地区：[1]上海大学微电子学院,上海200444 [2]中国科学院上海光学精密机械研究所信息光学与光电技术实验室,上海201800 [3]张江实验室,上海201210

出　　处：《光学学报》2024年第13期278-287,共10页Acta Optica Sinica

基　　金：项目受张江实验室支持。

摘　　要：为分析空间相干性对均匀性的准确影响,提出一种基于互强度传播理论的部分相干光刻照明仿真方法。在不同照明模式和同一照明模式以及不同部分相干因子的情况下,分析空间相干性对掩模面照明均匀性的影响。结果表明,照明均匀性会随着相干度增大而减小,散斑对比度会随着相干度增大而增大。为了满足浸没式193 nm光刻机均匀性大于97.5%的照明要求,环形、二极和四极照明的空间相干度应分别小于3.37%、2.96%和3.11%,对应的散斑对比度分别小于2.81%、2.13%和2.33%。Objective The model for deep ultraviolet lithography illumination systems is typically simplified. Studies have assumed that the illumination beam propagates as a set of plane waves within a given angular range, with each plane wave considered to be incoherent. Here, “incoherent” means that when calculating intensity by summing the squares of the complex amplitudes of the plane waves, the cross terms related to these complex amplitudes are disregarded, and only the squares of the complex amplitude modes are retained. This method is known as intensity superposition. Although any instantaneous light field superposition should theoretically be a superposition of complex amplitudes, the key factor for lithography exposure is the time-averaged intensity. Under incoherent conditions, the cross terms cancel each other out over time, thus they are omitted during incoherent superposition. However, this approximate assumption relies on the source being completely spatially incoherent. Due to the limited exposure time in lithography and the spatial coherence of the lithography source, this assumption is not entirely accurate. The intensity distribution on the image plane results from the coherent superposition of diffracted light from a finite size of a microlens unit and diffracted light from other microlens units illuminating the target surface. When calculating light intensity, it is important to consider the influence of certain cross terms. Gregg et al. have published numerous academic papers on laser speckle and coherence effects on mask surfaces. However, due to the use of KrF or ArF excimer lasers in deep ultraviolet lithography machines, which have multiple transverse modes and low spatial coherence, the complex coherence mode between adjacent microlenses in the illumination pupil is no greater than 2.43%. This results in a negligible decrease in lithographic performance, a matter that has not garnered sufficient attention or discussion in the industry. In recent years, as research on lithography sources has de

关 键 词：物理光学 光刻 照明系统 空间相干性 照明均匀性 散斑 

分 类 号：TN305.7[电子电信—物理电子学]