The decreasing size of semiconductor features and the increasing structural complexity of advanced devices have placed continuously greater demands on manufacturing metrology, arising both from the measurement challenges of smaller feature sizes and the growing requirement to characterize structures in more than just a single critical dimension. For scanning electron microscopy, this has resulted in increasing sophistication of imaging models. For critical dimension atomic force microscopes (CD-AFMs), this has resulted in the need for smaller and more complex tips. Carbon nanotube (CNT) tips have thus been the focus of much interest and effort by a number of researchers. However, there have been significant issues surrounding both the manufacture and use of CNT tips. Specifically, the growth or attachment of CNTs to AFM cantilevers has been a challenge to the fabrication of CNT tips, and the flexibility and resultant bending artifacts have presented challenges to using CNT tips. The Korea Research Institute for Standards and Science (KRISS) has invested considerable effort in the controlled fabrication of CNT tips and is collaborating with the National Institute of Standards and Technology on the application of CNT tips for CD-AFM. Progress by KRISS on the precise control of CNT orientation, length, and end modification, using manipulation and focused ion beam processes, has allowed us to implement ball-capped CNT tips and bent CNT tips for CD-AFM. Using two different generations of CD-AFM instruments, we have evaluated these tip types by imaging a line/space grating and a programmed line edge roughness specimen. We concluded that these CNTs are capable of scanning the profiles of these structures, including re-entrant sidewalls, but there remain important challenges to address. These challenges include tighter control of tip geometry and careful optimization of scan parameters and algorithms for using CNT tips.

中文翻译：

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在临界尺寸原子力显微镜中评估碳纳米管探针。

半导体特征尺寸的减小和先进设备的结构复杂性的不断提高，对制造计量学提出了越来越高的要求，这既源于更小的特征尺寸的测量挑战，也越来越需要在不仅仅是一个关键尺寸的范围内表征结构。对于扫描电子显微镜，这导致成像模型的复杂性增加。对于临界尺寸原子力显微镜（CD-AFM），这导致需要更小，更复杂的吸头。因此，碳纳米管（CNT）的尖端已成为许多研究人员关注和努力的焦点。然而，在CNT尖端的制造和使用方面都存在重大问题。具体来说，碳纳米管在AFM悬臂上的生长或附着一直是制造碳纳米管尖端的挑战，而柔韧性和所产生的弯曲伪影则对使用碳纳米管尖端提出了挑战。韩国标准科学研究院（KRISS）在CNT尖端的受控制造方面投入了相当大的努力，并且正在与美国国家标准技术研究院合作，将CNT尖端应用于CD-AFM。通过使用操纵和聚焦离子束工艺，KRISS在精确控制CNT取向，长度和末端修饰方面取得的进展使我们能够为CD-AFM实现球形CNT尖端和弯曲CNT尖端。我们使用了两代不同的CD-AFM仪器，通过对线/空间光栅和编程的线边缘粗糙度样本进行成像，评估了这些尖端类型。我们得出的结论是，这些CNT能够扫描这些结构的轮廓，包括凹入侧壁，但是仍然存在重要的挑战需要解决。这些挑战包括对针尖几何形状的更严格控制以及对使用CNT针尖的扫描参数和算法的仔细优化。