19 November 2001 Nanoscale fabrication using single-ion impacts
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We describe a novel technique for the fabrication of nanoscale structures, based on the development of localized chemical modification caused in a PMMA resist by the implantation of single ions. The implantation of 2 MeV He ions through a thin layer of PMMA into an underlying silicon substrate causes latent damage in the resist. On development of the resist we demonstrate the formation within the PMMA layer of clearly defined etched holes, of typical diameter 30 nm, observed using an atomic force microscope employing a carbon nanotube SPM probe in intermittent-contact mode. This technique has significant potential applications. Used purely to register the passage of an ion, it may be a useful verification of the impact sites in an ion-beam modification process operating at the single-ion level. Furthermore, making use of the hole in the PMMA layer to perform subsequent fabrication steps, it may be applied to the fabrication of self-aligned structures in which surface features are fabricated directly above regions of an underlying substrate that are locally doped by the implanted ion. Our primary interest in single-ion resists relates to the development of a solid-state quantum computer based on an array of 31P atoms (which act as qubits) embedded with nanoscale precision in a silicon matrix. One proposal for the fabrication of such an array is by phosphorous-ion implantation. A single-ion resist would permit an accurate verification of 31P implantation sites. Subsequent metalisation of the latent damage may allow the fabrication of self-aligned metal gates above buried phosphorous atoms.
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Victoria Millar, Victoria Millar, Chris I. Pakes, Chris I. Pakes, Alberto Cimmino, Alberto Cimmino, David Brett, David Brett, David N. Jamieson, David N. Jamieson, Steven D. Prawer, Steven D. Prawer, Changyi Yang, Changyi Yang, Bidhudutta Rout, Bidhudutta Rout, Rita P. McKinnon, Rita P. McKinnon, Andrew S. Dzurak, Andrew S. Dzurak, Robert G. Clark, Robert G. Clark, } "Nanoscale fabrication using single-ion impacts", Proc. SPIE 4590, BioMEMS and Smart Nanostructures, (19 November 2001); doi: 10.1117/12.454601; https://doi.org/10.1117/12.454601

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