CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Deliverables
The nano-nozzle hole is drilled into a microstructured hollow pyramid in the rear of the pyramid by means of a focused ion beam (FIB). The FIB is aligned to the apex of the pyramid with the four sharp edges formed by the 111-plane wet etching process of the pyramid. The breakthrough phase of the milling process demonstrates clearly the physical, momentum exchange based nature of this process. The shape of the drilled hole is determined by the beam profile of the FIB. For fabrication of the nozzles a MICRION 2500 FIB system was used, and the ion beam currently used for milling the apertures was about 2 µA. With this assembly, high-resolution nozzles with aperture sizes under 100 nm were manufactured.
The disadvantage of serial writing techniques, which are more time consuming than parallel printing techniques, can be overcome by building up arrays of the writing units. For this purpose arrays of nanonozzles were fabricated, allowing for multi-jet structuring of a work piece. Distances of the apertures are 300 µm to each other. This makes possible a parallel structuring of substrate areas of 300 µm x 300 µm. After drilling the nozzles, the silicon pyramids are covered with an evaporated chromium and gold layer system each of 50 nm thickness, to protect them against the reactive etching gases.
Transport of free radicals through high aspect ratio structures and their interaction with the substrate are investigated. The results are also applicable to the deep etching of silicon or polymeric materials by utilising a novel method for pattern generation and micro-fabrication using scanning micro/nanonozzles. Electrically neutral radicals created in a µ-wave plasma discharge are pumped through a small tube tapered to a nozzle and directed on the substrate. Due to a small distance between the nozzle and the surface of the substrate, a localised interaction is induced.
Direct nanostructuring with a jet of neutral radicals, driven only by a pressure gradient, was demonstrated. High etching rates without ion bombardment and damaging the crystal structure of the substrate are achieved by using a high-density radical source and an elaborate transportation system.
We developed a new type of tool for nanofabrication, namely atomic force microscopy combined with nanoscale localised chemical etching by gaseous radicals. Reactive species created in a plasma source are pumped through a capillary that is pulled to form a nanonozzle. The electrically neutral radicals are forced in the direction of the substrate just by a pressure gradient along the tube.
Due to the high directionality of the particle beam emerging from the high aspect ratio nanonozzle, a strongly localised etching or deposition is induced. By scanning the substrate a small distance under the nozzle, a pattern generation with nearly the same resolution as the nozzle diameter is performed.
By means of a sub-100 nm hollow tip acting also as a scanning nanoprobe, this technology provides an instrument for simultaneous in-situ structuring and imaging. The addressing of the nozzle and therefore the placing of the chemical reaction on the substrate is performed by a standard AFM positioning system. Thus, the outlined active AFM-sensor, which locally delivers radicals with high resolution and acts as a probe tip at the same time, is capable to "read" and "write" simultaneously.
The integration of the Nanojet technology in a vacuum AFM-system leads to a versatile tool for multi-radical-beam micro- and nanostructuring with manifold applications in IC-producing industry, physics, chemistry and biology.
The radicals are created in a µ-wave plasma generator, based on a cavity, powered by an EMS microtron 200 microwave generator (100 W at 2.45 GHz). The cavity surrounds a quartz tube with an inner diameter of 19 mm. The cavity design of the plasma generator leads to a high degree of dissociation of the process gases, thereby providing a high-density source of radicals, due to efficient excitation and ionisation in the standing µ-waves. Impedance matching is achieved by a short circuit plunger. Process parameters are 50 sccm flow rate SF(6) and 30 sccm Oxygen, respectively, at a plasma pressure of 2.2 mbars, for the etching of silicon with rates up to 0.8 µm/min and 200 sccm Oxygen, 0.25 sccm SF(6), at a pressure of 4.7 mbars, for the etching of polymers with rates up to 0.4 µm/min.
The plasma chamber tube is tapered to a smaller tube with a diameter of 2.6 mm guiding the radical stream to the nozzle. High radical lifetimes and therefore transportation over long distances can be achieved by the proper choice of the tube materials with respect to the recombination probability on the surface (i.e. quartz in this case) and the geometrical layout of the transport tube taking into account the optimum plasma parameters for efficient radical generation. Pressure in the reaction chamber is < 5x10-4 mbars, thus, a directed jet stream is maintained by the large differential pressure between plasma and reaction chamber.
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