Process windows based on Mean CD (“Critical Dimension”) have been an analysis workhorse for estimating and comparing the robustness of semiconductor microlithography processes for more than 30 years. While tolerances for variation of CD are decreasing in step with the target CD, the acceptable number of printed defects has remained flat (Hint: Zero) even as the number of features increases quadratically. This disconnect between two key process estimators, CD variability and defect rate, must be addressed. At nodes that require EUV lithography, estimating the printed defects based solely on a Mean CD process window is no longer predictive. The variability / distribution of the printed CDs must be engineered so that there are no failures amongst the billions of instances, rendering the Mean CD, often measured on just hundreds or thousands of instances, a poor predictor for outliers. A “defect-aware” process window, where the count of printed defects is considered in combination with more advanced statistical analysis of measured CD distributions can provide the needed predictability to determine whether a process is capable of sufficient robustness. Determining process robustness where stochastics and defects are taken into account can be simplified by determining the CD process margin. In this work we study dense via/contact hole arrays exposed with 0.33NA single exposure EUV lithography after both the lithography and etch steps. We describe a methodology for expanding the analysis of process windows to include more than the mean and $3{{\sigma }}$ of the data. We consider the skew and kurtosis of the distribution of measured CD results per focus-exposure condition and compare/correlate the measured CD process window results to the CD process margin.

中文翻译：

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了解缺陷感知过程窗口中局部可变性的重要性

30 多年来，基于平均 CD（“临界尺寸”）的工艺窗口一直是评估和比较半导体微光刻工艺稳健性的分析工具。虽然 CD 变化的容差随着目标 CD 逐步减少，但即使特征数量呈二次方增加，可接受的印刷缺陷数量也保持不变（提示：零）。必须解决两个关键过程估算器（CD 可变性和缺陷率）之间的脱节问题。在需要 EUV 光刻的节点上，仅根据平均 CD 工艺窗口估计印刷缺陷不再具有预测性。必须设计打印 CD 的可变性/分布，以便在数十亿个实例中没有故障，呈现平均 CD，通常仅在数百或数千个实例上进行测量，对于异常值的预测效果不佳。“缺陷感知”工艺窗口，结合更高级的测量 CD 分布统计分析考虑印刷缺陷的数量，可以提供所需的可预测性，以确定工艺是否具有足够的稳健性。通过确定 CD 工艺裕度，可以简化在考虑随机性和缺陷的情况下确定工艺稳健性。在这项工作中，我们研究了在光刻和蚀刻步骤后使用 0.33NA 单次曝光 EUV 光刻曝光的密集通孔/接触孔阵列。我们描述了一种方法，用于扩展过程窗口的分析，以包括数据的平均值和 $3{{\sigma }}$。