Nanotechnology for engineers Summer semester 2004-2005 SPM lithography 1 Nanotechnology for Engineers : J. Brugger (LMIS-1) & P. Hoffmann (IOA) Microfabricated tools for nanotechnologies Surface modification using SPM • the nature of the interaction determines the sample property that is observed • the magnitude of the interaction determines whether we observe or modify: SPM as a microscope or a tool interaction 2 1 Microfabricated tools for nanotechnologies SPM Lithography various interaction with sample • high resolution (clearly sub-100nm) • 3D capable (slight topography compensate with flexible beam) • parallel approach (gain speed) • examples: – – – – field enhanced oxidation resist exposure Dip-Pen/NADIS lithography (physico-chemical) Scanning nanostencil 3 Microfabricated tools for nanotechnologies Nanostructures made by AFM probe Compact Disc 1 µm 4 2 Microfabricated tools for nanotechnologies SPL (1) Field Enhanced Oxidation Picture and text from: Quate Group, Stanford A voltage bias between a sharp probe tip and a sample generates an intense electric field at the tip. The high field can be used to locally oxidize silicon in a process known as electric-field-enhanced oxidation. The high field desorbes the hydrogen passivation on the silicon surface, allowing the exposed silicon to oxidize in air (the oxidation rate is enhanced by the presence of the accelerating field). Both single-crystal silicon and amorphous silicon may be locally oxidized in such a way. This local oxidation process is powerful because of its fine resolution (sub-50-nm) and the resistant oxide etch mask that is created. Our work involves characterizing the oxidation process, increasing pattering reliability and throughput, and fabricating structures and devices using this local oxidation technique. 5 Microfabricated tools for nanotechnologies SPL (1) Field Enhanced Oxidation with 50 levers in parallel Oxidation of silicon with 50 probes. Probes are spaced by 200 um and each was used to draw a single line 1 cm long. The full patterned area spans 1 cm x 1 cm. The blue box in the lower left corner of the image depicts the typical scan area of a commercial AFM (100 um x 100 um). From: Quate Group, Stanford 6 3 Microfabricated tools for nanotechnologies SPL (2) Exposure of resist From: Quate Group, Stanford Electron exposure of a resist material, such as an organic polymer or a monolayer resist using field-emission from the tip (induce chemical changes). 7 Microfabricated tools for nanotechnologies SPL (2) Exposure of resist (3D capable) 100-nm pMOSFET Fabrication Gate Lithography Uniform 100-nm Gate Over Topography From: Quate Group, Stanford 8 4 Microfabricated tools for nanotechnologies Dip-Pen Nanolithography Writing >30 nm lines on Au surface using 1-othodecanethiol as ink Chad A. Mirkin et al. Science 283, 661 (1999) 9 Microfabricated tools for nanotechnologies Nanoscale Dispensing • pattern “liquids”, e.g. biomolecules, suspensions, “surface chemistry”, ... • • versatile (ambient conditions) parallel probes for multi-material deposition integration of fluidic system possible • 10 5 Microfabricated tools for nanotechnologies Nanoscale Dispensing – FIBbed probes material to deposit probe with apertured tip deposition of drops by touching substrate reservoir 2nd generation probes prepared by FIB milling tip/apert. head-on tip 1st approach: no approach snap-in indicating clean surface array with 1.0 µm pitch, drops separated array with 0.5 µm pitch, drops collapsed onto one 2nd & more approaches: snap-in distance 100nm corresp. to drop height glycerol on SiO2, image size 10 µm x 10 µm dots size 50 – 100 nm 11 Microfabricated tools for nanotechnologies Parallel Probe Dispensing • Array of 4 cantilevers with passivated aluminum electrodes for electrowetting • Deposition of two different solutions with the same cantilevers CNRS Toulouse 12 6 Microfabricated tools for nanotechnologies Parallel Dispensing CNRS Toulouse 13 Nanotechnology for engineers Summer semester 2004-2005 AFM nanostencil 14 Nanotechnology for Engineers : J. Brugger (LMIS-1) & P. Hoffmann (IOA) 7 Microfabricated tools for nanotechnologies Scanning AFM nanostencil FIB modified AFM cantilever tip A evaporation source B light source C light detector (PSD) D cantilever E sample IBM Zurich Research Laboratory Roli Luthi et al. APL 75, n. 9, 1999 15 Microfabricated tools for nanotechnologies Scanning AFM nanostencil Unique feature: Variable thickness as function of scan speed. • Metal deposition • Atomically clean • Easy relocation • AFM images and patterning with same cantilever 200 nm 90 nm Cu nanowire Cu nano-ring width < 90 nm, height 4 nm width < 200 nm, height 20 nm R. Luthi et al. APL 75, n. 9, 1999 16 8
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