Collaborative Research: Defect-free nano fabrication of plasmonic structures

Morehouse College, Atlanta GA

Investigators

Abstract

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.