NiSi Nanowires and Nanobridges Formed by Metal-Induced Growth
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0901-Ra22-03-Rb22-03.1
NiSi Nanowires and Nanobridges Formed by Metal-Induced Growth
Joondong Kim, Dongho Lee, and Wayne A. Anderson University at Buffalo, State University of New York, Department of Electrical Engineering, Buffalo, NY 14260 USA
ABSTRACT Nickel monosilicide (NiSi) nanowires (NWs) were fabricated by metal-induced growth at 575 oC. The solid-state reaction of Ni and Si provides linear grown NWs. The parallel grown NW forms a nanobridge (NB) across a trench, patterned with a simple optical lithography and metal lift-off method. The Ni pads gave a good Ohmic contact without affecting the I-V transport characteristics through a NB. The metallic NB, 2.73 µm in length and 50 nm in diameter, gave a low resistance of 148 Ω . The selfassembled 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) are attractive entities as one-dimensional building blocks for use in nanoelectronics and nanoscale connections. Use of NWs may be a breakthrough to overcome the difficulty in scaling down of integrated circuits. The first and inevitable step of nanoelectronics integration is to form contacts. The various approaches to NB or NW connections have been performed by guided self-assembly using SiO2 patterning and cracking [1], field-emission induced growth on a scanning tunneling microscopy tip [2], ac or dc electric field [3], bridging of granular films [4], chemical vapor deposition growth [5] and electron beam lithography [6]. In considering cost and simplicity, it is desirable to be independent from the use of complex and multiple lithography steps. Moreover, Ni monosilicide (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
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resistive C54 phase. CoSi2 is limited by high Si consumption and junction leakage. NiSi is a promising material to substitute for those silicide materials providing several advantages; low resistivity, lower Si consumption and lower formation temperature [7]. These merits prompt interest in NiSi nanowires to make a 1 dimensional nanoscale building block. We present here metal-induced grown NiSi NWs and nanobridges (NBs) in a trench fabricated by simple optical lithography and metal lift-off. EXPERIMENTAL DETAILS Si wafers cut as 1 cm × 1.5 cm Si were chemically cleaned by acetone, methanol, and DI water. A 200 nm layer of SiO2 was deposited by plasma enhanced chemical vapor deposition (PECVD) as a diffusion barrier and an insulation layer. After coating SiO2 on the Si wafer, primer was applied for 10 seconds and spun for 10 seconds. The photoresist (PR) was spun at 5000 rpm for 30 seconds to have a 1 µm thickness. The PR coated sample was prebaked, to improve adhesion and remove solvent,
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