Spontaneous Growth of Nickel Silicide Nanowires and Formation of Self-Assembled Nanobridges by the Metal Induced Growth
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Spontaneous Growth of Nickel Silicide Nanowires and Formation of SelfAssembled Nanobridges by the Metal Induced Growth Method
Joondong Kim1, Wayne A. Anderson1 and Young-Joo Song2 1
Department of Electrical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA 2
High-Speed SoC team, Electronics and Telecommunications Research Insititute, Yuseong-gu, Daejeon, 305-350, Korea
ABSTRACT Nickel monosilicide (NiSi) nanowires (NWs) have been fabricated by the metal induced growth (MIG) method. Ni as a catalyst was deposited on a SiO2 coated Si wafer. In a DC magnetron sputtering system, the Ni reacts at 575 oC with sputtered Si to give nanowires. Different metal catalysts (Co and Pd) were used to prove the MIG NW growth mechanism. NiSi NWs were a single crystal structure, 20-80 nm in diameter and 1-10 µm in length. The linear NW growth property provided nanobridge formation in a trenched Si wafer. The trenches in a Si wafer were made by dry etching and a simple, conventional metal lift off method. The self-assembled nanobridge can be applied to form nanocontacts at relatively low temperatures. The MIG NB is a promising 1 dimensional nanoscale building block to satisfy the need of ‘self and direct’ assembled ‘bottom-up’ fabrication concepts.
INTRODUCTION Nanowires (NWs) and nanotubes (NTs) are attractive entities as 1 dimensional building blocks to use in nanoelectronics and nanoscale connections. The interest in NWs has been increased to overcome the limits of NTs and use NWs as nanodevices [1]. The bottom-up approach provides cost-effective nanowires compared to the top-down approach [2] and offers much promise in future integrated circuits [3]. The self and directed assembly method based on the bottom-up process will inaugurate the volume manufacturing of nanotechnology [4]. The nanobridge (NB) is a basic and essential connection route as a 1 dimensional building block in deep submicron or nanoelectronic devices. The various approaches to NB or NW connections have been performed by
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guided self-assembly using SiO2 patterning and cracking [2], field-emission induced growth on a scanning tunneling microscopy tip[5], ac or dc electric field [6], bridging of granular films [7], chemical vapor deposition growth [8] and electron beam lithography [9]. It is desirable to fabricate the nanoscale connections by a one step process with less complexity and high reproducibility at low cost. This paper shows the mechanism of the nanowire growth and illustrates a straightforward method to form nanowire bridges by Metal Induced Growth (MIG).
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 before loading for DC magnetron sputtering. In the sputtering process, Si was sputtered on the Ni layer at a substrate temperature of 575 oC. To form NBs, a dry etching system (Applied
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