Uncertainty Estimation and Design Optimization of 2D Diffraction-Based Overlay Metrology Targets,ACS Photonics

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Uncertainty Estimation and Design Optimization of 2D Diffraction-Based Overlay Metrology Targets
ACS Photonics ( IF 6.5 ) Pub Date : 2020-08-26 , DOI: 10.1021/acsphotonics.0c00911
Ruslan Röhrich _{1,

2} , Giorgio Oliveri ₁ , Stefanos Kovaios ₁ , Vasco T. Tenner _{2,

3,

4} , Arie J. den Boef _{2,

3,

4} , Johannes T. B. Overvelde ₁ , A. Femius Koenderink ₁

Affiliation

Scatterometry is an optical metrology technique in which light scattered from a specifically designed grating stack (overlay target) is measured in the far-field. Using 1D periodic overlay target designs, the technique has been shown to have nanometer-scale sensitivity to spatial misalignments of subsequent patterned layers, which are also known as overlay errors. However, while scatterometry is highly sensitive to overlay errors, multiple sources of systematic errors hinder its absolute accuracy. Here, we investigate how an extended version of scatterometry called Fourier scatterometry, in combination with more complex overlay target designs, can help addressing those challenges. To this end, we developed a statistical method that can determine the influence of 2D overlay targets on the overlay measurement uncertainty. We study periodic and deterministic aperiodic designs as well as designs that emerged from simulated annealing optimizations. Our results suggest that current overlay target designs could be augmented by more complex 2D designs to fulfill specific purposes, such as fabrication robustness and high sensitivity over a large overlay range.

中文翻译：

基于二维衍射的重叠计量目标的不确定度估计和设计优化

散射测量是一种光学计量技术，其中，在远场中测量从专门设计的光栅堆（叠加目标）散射的光。使用一维周期性重叠目标设计，该技术已显示出对后续图案化层的空间失准具有纳米级灵敏度，这也称为重叠误差。但是，尽管散射测量法对叠加误差非常敏感，但系统误差的多种来源阻碍了其绝对精度。在这里，我们研究称为傅立叶散射的散射测量的扩展版本，结合更复杂的叠加目标设计，如何帮助应对这些挑战。为此，我们开发了一种统计方法，可以确定2D重叠目标对重叠测量不确定度的影响。我们研究周期性和确定性的非周期性设计，以及从模拟退火优化产生的设计。我们的结果表明，可以通过更复杂的2D设计来增强当前的覆盖目标设计，以实现特定的目的，例如在较大覆盖范围内的制造鲁棒性和高灵敏度。

更新日期：2020-10-21

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