EUV口罩的EUV散射测量和有限元分析
Metrology of EUV Masks by EUV-Scatterometry and Finite Element Analysis
摘要：
极紫外（EUV）光刻技术被认为是生产下一代计算机技术的主要候选技术。由于EUV光的波长较短（约13 nm），因此必须在生产过程中使用新型反射掩模。满足这些EUV掩模的高质量要求的先决条件是用于吸收体图案轮廓表征的简单且准确的方法。在我们以前的工作中，我们证明了有限元法（FEM）是非常适合的EUV散射测量的模拟，可以用来重建EUV掩模轮廓从实验散射测量数据。在这篇文章中，我们将间接计量方法应用于在大范围的占空比（1：2，...，1：20）。我们定量比较重建的吸收模式参数直接AFM和CD-SEM测量得到的值。我们分析的可靠性重建给定的实验数据。对于吸收线的CD，比较显示出1 nm量级的一致性。此外，我们讨论了特殊的数值技术，如区域分解算法和高阶有限元及其快速和准确的反问题的解决方案的重要性。
英文摘要：
Extreme ultraviolet (EUV) lithography is seen as a main candidate for production of future generation computer technology. Due to the short wavelength of EUV light (around 13 nm) novel reflective masks have to be used in the production process. A prerequisite to meet the high quality requirements for these EUV masks is a simple and accurate method for absorber pattern profile characterization. In our previous work we demonstrated that the Finite Element Method (FEM) is very well suited for the simulation of EUV scatterometry and can be used to reconstruct EUV mask profiles from experimental scatterometric data. In this contribution we apply an indirect metrology method to periodic EUV line masks with different critical dimensions (140 nm and 540 nm) over a large range of duty cycles (1:2, ..., 1:20). We quantitatively compare the reconstructed absorber pattern parameters to values obtained from direct AFM and CD-SEM measurements. We analyze the reliability of the reconstruction for the given experimental data. For the CD of the absorber lines, the comparison shows agreement of the order of 1nm. Furthermore we discuss special numerical techniques like domain decomposition algorithms and high order finite elements and their importance for fast and accurate solution of the inverse problem.
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