Multi layer overlay measurement recent developments
Multi layer overlay measurement recent developments
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多层叠加测量最新进展
DOI：
10.1117/12.2025865
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
P. Leray
中科院分区：
文献类型：
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作者：
Nuriel Amir;N. Shuall;Inna Tarshish;P. Leray
随着光刻层数的不断增加，尤其是多模化，主要的挑战之一是能够同时对齐多个层。在过去，事情很简单，设置对齐树以便每个层对齐到一个层，并且最多测量两个层，例如接触到poly和隔离。今天，即使在20nm节点上，对于隔离层、聚层、接触层和金属1层等关键层，也存在双重和三重图案。这将导致更加复杂的对齐树和覆盖（OVL）测量。层有时与前一层的平均值对齐，与不同方向的不同层对齐，并且根据几次测量完成配置。这一不断增长的挑战显著增加了覆盖测量的数量，增加了目标面积，并且需要使来自不同层的许多测量保持一致。另一个挑战是在开发过程中食谱数量的增加和对灵活的对齐树方案的需求。这些挑战是由多层目标解决的，如三重目标、多层目标、开花和微开花目标，其中来自多个图案步骤和图层的对齐标记密集。单个OVL读数由计量工具在选定的一对或多对平均值上计算1。在这里，我们提出了多层测量，它提供了额外的计量和解决这些挑战：在一次测量中实现了多个叠加结果，结果总是自一致的。它允许在相同的测量抓取回看和处置前层后，他们的处理完成。它允许一个灵活的对准树，无需添加或改变目标，即使在斜坡和生产。它减少了需要创建和管理的食谱的数量。它还大大减少了目标所需的面积。在本文中，我们将展示IMEC在四层后端（BE）堆栈上的最新结果，其中包括一个双图案层。我们比较了几种目标尺寸，表明这种目标可以满足10x10 μm的Indie要求。结果表明，为了获得良好的多层测量，不需要在性能上做出很大的妥协。最后，我们将描述在前端（FE）层中更需要的过程兼容目标。展望未来节点和多节距分裂光刻所需的复杂性增加，令人鼓舞的是，对于Overlay，我们可以简化计量，而不是使其遵循复杂性趋势。
One of the main challenges related to the growing number of Litho layers and most specifically to Multi Patterning, is the ability to align to many layers at once. In the past things were simple, the alignment tree was set so that every layer aligns to one layer and at the most is measured versus two layers, such as contact to poly and Isolation. Today, even at the 20 nm node there are double and triple patterning for critical layers such as Isolation, poly, contact and Metal 1. This forces a much more complex alignment tree and Overlay (OVL) measurement. Layers are sometimes aligned to an average of previous layers, to different layers at different orientations and disposition is done based on several measurements. This growing challenge increases the number of Overlay measurements significantly, increases the target area and present the need to make many measurement from different layers consistent. Another challenge is the increased number of recipes and the need for flexible alignment tree scheme during development. These challenges are addressed by Multi layer targets such as Triple AIM, Multilayer AIMid and the Blossom and micro-Blossom targets where alignment marks from multiple patterning steps and layers were densely populated. A single OVL reading is calculated by the metrology tool on a selected pair or multiple pair average1. Here we propose the Multi-Layer measurement that provides an additional degree of metrology and solution to these challenges: in one measurement several overlay results are achieved, the results are always self-consistent. It allows at the same measurement grab to look back and disposition previous layers after their processing was completed. It allows a flexible alignment tree without the need to add or change targets, even during ramp and production. It reduces the number of recipes that need to be created and managed. And it also reduces significantly the area needed for the targets. In this paper we will show recent results from IMEC, on Back-End (BE) stack of four layers including one double patterning layer. We compared several target sizes, showing that such a target can fit within the Indie requirements of 10x10 μm. Results show that there is not a lot of need to compromise on performance in order to get good Multi-Layer measurements. Eventually we will describe process compatible targets which are needed more in the Front End (FE) layers. Looking forward at the increased complexity needed for future nodes and multiple pitch splitting lithography, it is encouraging to see that for Overlay we can simplify metrology instead of making it follow the complexity trend.