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题名	极紫外光刻掩模建模与缺陷补偿方法研究
作者	刘晓雷
学位类别	博士
答辩日期	2015
授予单位	中国科学院上海光学精密机械研究所
导师	王向朝
关键词	极紫外光刻 掩模模型 缺陷补偿 图形偏移 吸收层修正
其他题名	Study on Mask Modeling and Defect Compensation Method in Extreme Ultraviolet Lithography
中文摘要	光刻是极大规模集成电路制造的核心工艺，光刻分辨率决定集成电路芯片的特征尺寸。极紫外光刻通过减小曝光波长提高光刻分辨率，被认为是最有前景的下一代光刻技术。掩模缺陷尤其是多层膜缺陷是阻碍极紫外光刻实现量产的主要障碍之一。多层膜缺陷位于多层膜内部，在不破坏多层膜的情况下难以进行有效修复，需要通过一定的方法补偿缺陷对光刻成像的影响。图形偏移法与吸收层修正法是常用的两种缺陷补偿方法。图形偏移量和图形修正量分别是决定图形偏移法和吸收层修正法实施效果的关键参数。目前还没有有效的最佳图形偏移量确定方法。图形修正量通过多次掩模衍射场仿真求得。严格仿真方法可以准确仿真掩模衍射场分布，但计算量大，计算速度慢；现有的快速仿真模型在大幅牺牲仿真精度的前提下有效提高了仿真速度，或者保证了一定的仿真精度但仿真速度受限，难以满足快速高精度缺陷补偿的需求。为实现快速高精度缺陷补偿，本文对极紫外光刻掩模建模与缺陷补偿方法进行了研究，主要内容包括以下几个方面： 1.建立了一个基于单平面近似的极紫外光刻含缺陷多层膜仿真简化模型，实现了含高斯型缺陷多层膜衍射谱的快速准确仿真。与改进单平面近似模型相比，仿真速度基本一致的情况下，本模型提高了含缺陷多层膜衍射谱的仿真精度。6°入射时，衍射谱中0~+3级衍射光的振幅仿真误差减小50%以上。将该含缺陷多层膜模型与吸收层的薄掩模修正模型结合，建立了含缺陷掩模仿真简化模型，为实现高斯型缺陷的补偿奠定了技术基础。 2.建立了一个基于等效膜层法的极紫外光刻含缺陷多层膜快速仿真模型，实现了含缺陷多层膜衍射谱的准确快速仿真。与波导法严格仿真相比，对200 nm周期多层膜的仿真速度提高9倍左右。与改进单平面近似模型和基于单平面近似的简化模型相比，6°入射时，本模型对多层膜衍射谱+1级衍射光振幅的仿真误差分别减小了77%和63%。将该含缺陷多层膜模型与吸收层的薄掩模修正模型结合，建立了含缺陷掩模快速仿真模型，为实现缺陷补偿奠定了技术基础。 3.研究了基于图形偏移法的缺陷补偿方法，提出了基于缺陷影响最小化和基于缺陷覆盖数目最大化的最佳偏移量确定方法。以包含20个缺陷的掩模为例进行了仿真实验验证。采用最小化缺陷影响法确定偏移量之后，缺陷影响降低为无偏移时的5.7%，缺陷数目减少为8个；采用最大化缺陷覆盖数目法确定偏移量之后，缺陷数目减少为4个，缺陷影响降低为无偏移时的19.3%。结果表明，采用上述两种方法确定最佳偏移量后，缺陷影响均得到有效补偿。 4.研究了基于吸收层修正法的缺陷补偿方法，提出了一种计算最佳图形修正量的方法。采用基于单平面近似的简化模型计算最佳图形修正量，对缺陷造成的光强损失进行补偿。以22 nm接触孔图形为例进行了仿真实验验证。与采用严格仿真计算最佳图形修正量的方法相比，本方法得到了基本相同的最佳图形修正量，同时计算速度提高10倍以上。仿真结果表明，本方法有效提高了最佳图形修正量的计算速度。
英文摘要	Lithography is the key technology in the manufacturing of ultra-large scale integrated circuits. Resolution of lithograpy determines the critical dimension of the integrated circuits. Extreme Ultraviolet (EUV) lithography which scales the resolution by using short exposure wavelength is considered to be one of the most promising Next-Generation Lithographys. Mask defects, especially multilayer defects, are a major roadblock to EUV lithography adoption in high volume manufacturing. Defects inside multilayer stack are hard to repair without damaging the multilayer itself. Therefore, a methodology that is able to deal with defective masks is required. Pattern shifting method and absorber modification method are frequently used for defect compensation. Compensation results of these two methods depend on pattern shift and modification size, respectively. However, there is not yet a practical method to determine the optimal pattern shift. The modification size is calculated by simulating mask spectrum repeatedly. The rigorous method can be used for accurate mask simulation, but it is always complex and time-consuming. The fast models either accelerate the mask simulation at the cost of low accuracy, or guarantee the accuracy of simulation at the cost of poor accelaration. These make the simulation models difficult to meet the requirement of defect compensation. In this dissertation, mask modeling and defect compensation methods are studied. The following contents are covered: i.A simplified model based on single surface approximation (SSA) is built to simulate diffraction spectrum of multilayer that contains Gaussian defect in EUV lithography. Compared with advanced SSA model, simulation accuracy of the proposed model is improved, while the simulation speed is the same. The simulation errors of the amplitudes of 0~+3 orders of the spectrum are decreased by more than 50% at 6° incidence angle. A simplified model for simulating defective mask is built by combining the proposed multilayer model with modified thin mask model of the absorber, which lays the foundation for the compensation of Gaussian defect. ii.A fast model based on the equivalent layer method is built to simulate diffraction spectrum of defective multilayer in EUV lithography. Compared with Waveguide method, as the multilayer size is 200 nm, the simulation speed of the proposed model is improved nearly 9 times. Compared with advanced SSA model and the simplified model, the simulation errors of the amplitudes of +1 order of the spectrum calculated by the proposed model are decreased by 77% and 63% at 6° incidence angle, respectively. A fast model for simulation of defective mask is built by combining the proposed multilayer model with modified thin mask model of the absorber, which lays the foundation for the defect compensation. iii.The compensation method based on pattern shifting is studied. Two methods to determine the optimal pattern shift are proposed. These two methods are based on minimizing defect impact and maximizing number of covered defects, respectively. Taking a mask that contains 20 defects as an example, the defect impact is decreased to 5.7% of that without shifting, and the number of uncovered defects is reduced to 8 after minimizing defect impact. The number of uncovered defects is reduced to 4, and the defect impact is decreased to 19.3% of that without shifting after maximizing number of covered defects. The results show that the defect impact is decreased effectively after adopting the proposed methods. iv.The compensation method based on absorber modification is studied. A method to calculate the optimal modification size is proposed. The optimal modification size is calculated by using the simplified model based on SSA to compensate the loss of intensity caused by the defect. Taking 22 nm contact holes as an example, the optimal modification size calculated by the proposed method is the same as that calculated by the Waveguide method, while the computation speed of the proposed method is 10 times faster than that of the Waveguide method. It is demonstrated that the proposed method can speed up the calculation of the optimal modification size.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15933]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	刘晓雷. 极紫外光刻掩模建模与缺陷补偿方法研究[D]. 中国科学院上海光学精密机械研究所. 2015.

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