Morphological Changes while Growing Nickel Monosilicide Nanowires
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Morphological Changes while Growing Nickel Monosilicide Nanowires
Joondong Kim1, Wayne A. Anderson1, Elena A. Guliants2 and Christopher E. Bunker3 1
Department of Electrical Engineering University at Buffalo, State University of New York, Buffalo NY 14260 2 Energy & Environmental Science Division, University of Dayton Research Institute, Dayton, OH 45469 3 Propulsion Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433
ABSTRACT Nickel monosilicide (NiSi) nanowires (NWs) have been fabricated in a DC magnetron system by the Metal Induced Growth (MIG) method. The NW growing stages were sequentially observed by scanning electron microscopy. Deposited Ni on SiO2 coated Si wafers has been first grooved and agglomerated by thermal heating at 575 oC. In the sputtering procedure, Ni as a catalyst reacted with sputtered Si forming clusters. Nanowires were grown in the same directions on each cluster. Raman spectroscopy and Energy Dispersive Spectroscopy indicated the NW composition as NiSi. The linear propagating property of NWs was used to form self-assembled nanobridges (NBs) in trenched Si wafers. The affinity of NWs can be used on various substrate materials with less thermal damage. NiSi composed MIG-NBs are promising candidates as nanoscale contacts due to the features of low resistivity and low temperature processing giving less potential damage on fabricated structures.
INTRODUCTION NiSi has been intensively researched for use as a contact material of gate and source/drain in CMOS devices. It is superior to other candidates like TiSi2 and CoSi2. TiSi2 has difficulty in transformation of the C49 phase to the low resistive C54 phase [1]. CoSi2 is limited by high Si consumption and junction leakage [2]. These merits prompt interest in NiSi nanowires to make a 1-dimensional nanoscale building block. Previous research on Ni catalyzed NWs has been reported [3-4]. The low growth temperature of 320 to 420 oC is accomplished by decomposition of silane gas on Ni surfaces to make different composition (NiSi, Ni2Si and Ni3Si2) of NWs [3]. The amorphous NWs have been grown by a solid-liquid-solid mechanism at a high temperature of 950 oC to utilize the NiSi2 eutectic liquid droplets [4]. Recently, Ni diffusion on grown pure Si NWs to make NiSi junctions has been reported [5]. We
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present spontaneously grown NiSi NWs and self assembled NBs by the MIG method in the solid state reaction of Ni and sputtered Si. The MIG NWs and NBs are compatible with Si processing and the fabrication temperature is low to cause less damage on fabricated structures.
EXPERIMENTAL DETAILS A 200 nm SiO2 layer was first deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) acting as a buffer layer against Ni diffusion into the Si substrate. Ni as a catalyst metal was thermally evaporated onto a SiO2 coated Si substrate. Then, Si was deposited by DC magnetron sputtering onto the Ni layer at a substrate temperature of 575 oC. A dry etching system (Applied Materials, P-5000) was used to make tr
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