Multi-Ion Beam Lithography and Processing Studies
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Multi-Ion Beam Lithography and Processing Studies Bill R. Appleton1, Sefaattin Tongay1, Maxime Lemaitre1, Brent Gila1 , David Hays1, Andrew Scheuermann1, and Joel Fridmann2 1 2
NIMET Nanoscale Research Facility, University of Florida, Gainesville, FL. 32611 Raith USA, Inc., Ronkonkoma, NY, 11779
ABSTRACT. The University of Florida (UF) have recently collaborated with Raith Inc. to modify Raith’s ion beam lithography, nanofabrication and engineering (ionLiNE) station that utilizes only Ga ions, into a multi-ion beam system (MionLiNE) by adding the capabilities to use liquid metal alloy sources (LMAIS) to access a variety of ions and an EXB filter for mass separation. The MionLiNE modifications discussed below provide a wide range of spatial and temporal precision that can be used to investigate ion solid interactions under extended boundary conditions, as well as for ion lithography and nanofabrication. Here we demonstrate the ion beam lithographic capabilities of the MionLiNE for fabricating patterned arrays of Au and Si nanocrystals, with nanoscale dimensions, in SiO2 substrates, by direct implantation; and show that the same directwrite/maskless-implantation features can be used for in situ fabrication of nanoelectronic devices. Additionally, the spatial and temporal capabilities of the MionLiNE are used to explore the effects of dose rate on the long-standing surface morphological transformation that occurs in ion bombarded Ge. INTRODUCTION. The MionLiNE system shown in Figure 1 combines a precision scanned focused ion beam with a laser interferometer sample handling stage and lithographic patterning software for an integrated system that delivers mass-separated, multi-ion beams for processing. The system has a vacuum load lock for sample handling and an internal optical microscope to facilitate initial set up and navigation The actual ion column and its representative schematic are shown in Figure 2. The top flange holds the LMAIS that can be isolated from the rest of the system and LMAIS sources interchanged. The EXB Wien filter consists of a permanent magnet and a variable electric field. The permanent magnet is located outside the column/vacuum and is easily interchangeable should the desired ion
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Figure 1. MionLiNE system.
Figure 2. Schematic representation of the ion beam column optics, and an actual photograph of an installed system at right . selection require a different permanent field. The mass separation capability of the current filter is m/dm> 35, and the acceleration voltage can be adjusted from V= 15 – 40 kV. The LMAIS reported on in this paper is AuSi, and as the mass spectrum in Figure 3 shows it is possible to resolve singly and doubly charged ions as well as ion clusters of both Si and Au. Ion energies are E=qV where q is the ion charge, so doubly charged ions allows doubling the U = 35 kV Au U = 16.87 kV implantation energy; and ion clusters with 1 App. 1 = 1000 µm n atoms can provide reduced energies App. 2 = 40 µm Au Au E= qV/n as the atoms separate on entering Au the solid. Beam di
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