Collaborative Research: Defect-free nano fabrication of plasmonic structures

在过去的几十年里，令人印象深刻的光子技术的发展使具有难以想象的能力的新的革命性设备成为可能。现在有可能构思出能够检测单分子的高分辨率传感器，或者能够超过以前接受的分辨率极限的强大显微镜，甚至可以为实现使用光而不是电子的全光子计算机开辟一条清晰的道路。所有这些成就都有一个共同点：都利用了超材料的独特性质。超材料是在金属、半导体或它们的混合物中制造的纳米级结构，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设备的实施和广泛传播起到了重要作用。该项目提出了一种新的纳米结构的制备方法，由于其简单、低成本、健壮和高效，可以为促进超材料的广泛应用做出重大贡献。它承诺实现一种桌面图案工具，该工具可以很容易地在小型企业或实验室环境中与其他加工工具集成，并将有可能简化致力于高科技和纳米技术的小公司的运营，从而为社会带来好处。这项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(毫米平方毫米)上打印无缺陷的任意结构，曝光时间通常不超过一分钟。该方法将使用干涉光刻和Talbot自成像，结合高度相干的桌面极紫外激光，在多个样品上光学复制掩膜中定义的纳米结构。这种方法的新颖性在于利用了高度相干的极端紫外线桌面激光，结合经典的光学效应，将使纳米制造方法成为可能，具有以下独特特征：-无缺陷。这是一个独特的特征。原始光刻掩模上的任何缺陷都是在整个成像领域内平均的，所产生的打印基本上是无缺陷的。-紧凑型(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能力。-可伸缩。有了足够的照明，就有可能打印原始母版的去放大复制品。-健壮。因为口罩不与样品接触，所以它不会因使用而损坏或降级。-易于实现。掩膜和样品之间的工作距离非常大，通常只有几毫米，这有利于实验的建立。该装置只由衍射掩模和样品组成。成熟的紧凑型极紫外激光技术现在打开了一扇机会之窗，展示了一种纳米制造方法，这种方法以前由于缺乏足够大的平均功率相干源而不可行。利用所提出的光刻方法，在几分钟内就可以打印出具有任意动机和小于50 nm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 nm到13 nm)，因此可以想象这种方法将允许制造特征尺寸在几十纳米的纳米结构。

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.