Content | Omniprobe - Dallas, TX 75238 - 214-572-6800 AN-GIS-052411 © 2011 Omniprobe, Inc. All Rights Reserved Bright particles representing the iron catalyst are visible in this high angle annular dark field STEM image of a section of bundled CNTs that was GIS-ALD processed using t-butoxide and water. The lower left portion of the image contains a branch of CNTs low in catalyst density. The ALD coating on this branch is on the order of 10nm in thickness. Figure 3 Figure 4 30nm structures were created by ion beam induced deposition of tungsten hexacarbonyl using the OmniGIS® (courtesy of Neal Meyer and Arliena Holm, Hewlett Packard Corvallis). cycles of NO2 and NOx species to form a monolayer ring. Figure 3 shows the 10nm conformal aluminum oxide layer deposited by ALD on the CNT bundles, proving both the initialization and the ALD process were achieved. The OmniGIS® provides a powerful platform for direct write nanolithography applications within a FIB or SEM. The claimed minimum feature size for beam induced CVD from standard commercial dual beam systems is typically around 50nm. The drivers determining the tool capability are the beam process parameters (beam type (electrons or ions), spot size, accelerating voltage, current, beam source) and precursor gas delivery process parameters (carrier, flow, pressure, dispense proximity, source temperature). For optimal resolution, it is desirable to mimic the ALD process described earlier. This means sequentially adsorbing one monolayer of precursor onto the surface at a time and exposing the layer to the beam, thus depositing one monolayer at a time. Pulsing the gas approximates this effect and achieves 2-4x higher resolution or smaller minimum feature size than can be achieved with a continuous flow of precursor. With improved operator control of the precursor gas delivery, deposition of arrays of less than 20nm Pt features with approximately 1:1 spacing in a 20μm x 20μm array were achieved. Some of the arrays produced were large enough that the ion deposition rate with a 30kV 1pA beam resulted in a 24 hour run- time to complete the array; hence, most of the experimental work was performed using ion beam deposition. When doing e-beam deposition, it was found that pulsing the source gas resulted in faster deposition and crisper edges. Figure 4 shows an example of 30nm ion beam deposited structures using tungsten hexacarbonyl as the source. Experiments determined that pulsing of the source is critical to enable large arrays (25μm x 25μm) of 15-30nm features with 1:1 spacing. In general, the pulse rate must be higher if a carrier gas is not used, and the best pulsing scheme will vary as a function of the array size and feature size/spacing combination. Nanopatterning 1) Richard M Langford, Dogan Ozkaya, J Sheridan and Richard Chater (2004). Effects of Water Vapour on Electron and Ion Beam Deposited Platinum. Microscopy and Microanalysis, 10 (Suppl. 02) , pp 1122-1123 doi:10.1017/S1431927604883417 2) Principe, E. L., C. Hartfield, et al. (2008). Atomic Layer Deposition and Vapor Deposited SAMS in a CrossBeam FIB-SEM Platform: A Path To Advanced Materials Synthesis. Microscopy Today, 17: 18-25 3) Farmer, D. B. and R. G. Gordon (2006). “Atomic Layer Deposition on Suspended Single-Walled Carbon Nanotubes via Gas-Phase Non-covalent Functionalization.” NANO LETTERS 6(4): 699-703 |