Collaborative Research: Defect-free nano fabrication of plasmonic structures

在过去的几十年里，光子技术令人印象深刻的发展使具有不可想象的能力的新的革命性设备成为可能。现在有可能设想出能够检测单分子的高分辨率传感器，或者能够超越先前公认的分辨率限制的强大显微镜，甚至是实现使用光而不是电子的全光子计算机的明确途径。所有这些成就都有一个共同点：都利用了超材料的独特属性。超材料是由金属、半导体或它们的混合物制成的纳米级结构，它与激光脉冲相结合，开辟了一个全新的研究领域，使新的创新应用成为可能。快速获得可靠的纳米制造技术对这些新器件的实施和广泛传播起着重要作用。该项目提出了一种新的纳米级结构制造方法的发展，由于其简单，低成本，稳健性和效率，可以为促进超材料的广泛利用做出重大贡献。它承诺实现桌面图案工具，可以很容易地与小型企业或实验室环境中的其他处理工具集成，并且将有可能简化致力于高科技和纳米技术的小型公司的操作，从而造福社会。它还将通过将光学工程与计量学、激光设计和材料科学相结合的创新技术培训学生来影响教育。该研究项目将展示一种紧凑的（桌面）纳米制造工具，能够在大面积（毫米见方）上打印低于50nm特征尺寸的无缺陷任意结构，曝光时间短（通常不到一分钟）。该方法将使用干涉光刻技术和塔尔博特自成像技术，结合高相干台式极紫外激光器，在多个样品上光学复制掩模中定义的纳米结构。该方法的新颖之处在于利用高度相干的极紫外台式激光器，结合经典的光学效应，将使具有以下显著特征的纳米制造方法成为可能：这是一个独特的特点。原始光刻掩模上的任何缺陷都在整个成像场上平均，由此产生的打印基本上是无缺陷的。-紧凑（桌面）系统，可以为小型公司或大学研究实验室带来纳米图案化能力。-可伸缩。有了足够的照明，就有可能印出原画的缩小版复制品。——健壮。由于口罩不与样品接触，因此不会因使用而损坏或降解。-易于实现。掩模与样品之间的工作距离非常大，通常为几毫米，这便于实验设置。-琐碎对齐。该装置仅由衍射掩模和样品组成。紧凑的极紫外激光器的成熟技术现在为展示纳米制造方法打开了一扇机会之窗，这种方法在缺乏足够大的平均功率相干源之前是不可行的。采用所提出的光刻方法，可以在几分钟内打印任意动机和低于50nm临界尺寸的图案。由于图案的最小特征主要由照明的波长控制（激光的波长范围从47纳米到13纳米），因此可以想象，这种方法将允许制造具有几十纳米特征尺寸的纳米结构。

In the last decades the impressive development of photonic technology made possible new revolutionary devices with unthinkable capabilities. Now it is possible to conceive high-resolution sensors capable of single molecule detection, or powerful microscopes capable to surpass the previously accepted resolution limits, or even a clear path towards the realization of a fully photonic computer that will use light instead of electrons. All these accomplishments have a common denominator: all make use of the unique properties of meta-materials. Meta-materials are nano-scale structures fabricated in metals, semiconductors or in a mixture of them that combined with laser pulses had opened a whole new research area that enabled new innovative applications. Instrumental to the implementation and broad dissemination of these new devices is the rapid access to a reliable nano-fabrication technology. This project proposes the development of a new fabrication approach for nanoscale structures that due to its simplicity, lower cost, robustness and efficiency can make a significant contribution in facilitating the broad utilization of meta-materials. It promises the realization of a tabletop patterning tool that could easily be integrated with other processing tools in a small business or a laboratory environment, and will have the potential to simplify the operation of small companies dedicated to high tech and nanotechnology with the consequent benefit to society. It will also impact the education through the training of students in an innovative technology that combines optical engineering and metrology, laser design and material science.This research project will demonstrate a compact (tabletop) nano-fabrication tool capable of printing defect-free arbitrary structures with sub-50nm feature size, over large areas (millimeter square), with short exposure times (typically less than one minute). The approach will use interferometric lithography and Talbot self-imaging in combination with a highly coherent tabletop extreme ultraviolet laser to optically replicate nanostructures defined in a mask over multiple samples. The novelty of the method resides on the utilization of highly coherent extreme ultraviolet table-top lasers that combined with classical optical effects will make possible a nano-fabrication method with the following distinctive characteristics:- Defect free. This is a unique characteristic. Any defect on the original lithographic mask is averaged over the entire imaging field and the resulting print is essentially defect-free.- Compact (tabletop) system that can bring nano-patterning capabilities to small size companies or university research laboratories.- Scalable. With the adequate illumination, it is possible to print de-magnified replicas of the original master.- Robust. Because the mask is not in contact with the sample, it is not damaged nor degraded with usage.- Simple to implement. The working distance between the mask and the sample is very large, typically few millimeters, which facilitates the experimental set up.- Trivial alignment. The set up consists of only the diffractive mask and the sample.The mature technology of compact extreme ultraviolet lasers now opens a window of opportunity to demonstrate a nano-fabrication method that was not feasible before due to the lack of sufficiently large average power coherent sources. With the proposed lithography approach, it will be feasible to print, in a few minutes, patterns with arbitrary motives and sub-50nm critical size. Since the pattern's smallest feature is mainly controlled by the wavelength of the illumination (the laser's wavelengths range from 47nm to 13 nm) it is conceivable that this method will allow the fabrication of nanostructures with feature size in the few tens of nanometers.