Influences on accuracy of SEM based CD mask metrology with a view to the 32 nm node
Influences on accuracy of SEM based CD mask metrology with a view to the 32 nm node
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32 nm 节点对基于 SEM 的 CD 掩模测量精度的影响
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
A. Wiswesser
中科院分区：
文献类型：
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作者：
W. Häßler;C. G. Frase;D. Gnieser;H. Bosse;J. Richter;A. Wiswesser
扫描电子显微镜(SEM)今天被使用，在不久的将来也将被用作一种快速和高分辨率的测量方法，能够对最小的、孤立的和密集的特征进行表征，这些特征将被指定并在光掩模上产生，直到32 nm节点甚至更低。然而，已经证明，在不同的掩模吸收器组上基于扫描电子显微镜的CD测量结果可能显示出系统地依赖于不同CD-SEM设备之间的吸振器材料和其他堆栈参数。对于掩模制造环境中所要求的不同CD测量工具的适当的互相关，必须考虑这些掩模相关效应。在这篇文章中，我们将报告对当前和未来几代掩模上存在的线和空间特征的模拟和测量的扫描电子显微镜轮廓以及合适的测试结构的系统研究。研究包括扫描电子显微镜初级能量设置的变化，不同边缘算子对这些变化的响应，以及掩模特征的边缘角度的变化。这些模拟以蒙特卡罗方法为基础，并在适当的情况下辅之以其他现象学方法。由于掩模上必须相对于其尺寸进行控制的最小辅助特征与晶片上的最小特征尺寸大致相同，因此将针对小至32 nm的特征尺寸描述对扫描电子显微镜边缘对比度的模拟和不同CD-SEM边缘算法的响应。
Scanning electron microscopy (SEM) is used today and will be used also in the near future as a fast and high resolution measurement method capable to perform characterizations of the smallest isolated and dense features which are to be specified and produced on photomasks down to the 32 nm node and perhaps below. It has been demonstrated however, that SEM based CD metrology results on different mask absorber stacks may show systematic dependencies on the absorber materials and other stack parameters between different CD-SEM equipment. These mask dependent effects have to be taken into account for proper cross-correlation of different CD metrology tools, which is required in mask manufacturing environment. In this contribution we will report on systematic investigations of simulated and measured SEM profiles of line and space features present on current and future mask generations as well as on suitable test structures. The investigations comprise variations of SEM primary energy settings and the response of different edge operators on these variations as well as variations of edge angle of the mask features. The simulations are based on Monte Carlo methods which are supplemented by additional phenomenological approaches where appropriate. Simulations of SEM edge contrasts and the response of different CD-SEM edge algorithms will be described for feature sizes down to 32 nm, because the smallest assist-features on the mask which have to be controlled with respect to their dimensions are about the same size as the smallest feature sizes on the wafer.