Growth and Electrical Characterization of Horizontally Aligned CNTs

Abstract

Nickel catalyst nanoparticles acting as nucleating seeds for carbon nanotube (CNT) growth were selectively deposited on the sidewalls of titanium nitride (TiN) electrodes by electrochemical deposition (ECD) from a Ni 2+ electrolyte solution. Horizontal aligned CNTs were grown selectively from the sidewalls of these TiN electrodes forming a bridging CNT contact between the electrode gaps. Current-voltage measurements demonstrated this could be a promising technique towards nanoscale interconnections and nanoelectronic devices with resistance values for the bridging CNTs as low as 300 .To realise the potential of CNTs in microelectronic applications (1), sufficient control over their location and orientation should be demonstrated. Typically, control over the horizontal growth of CNTs has been achieved using controlled gas flows (2), electric fields (3) and CNT-surface interactions on faceted substrates (4). Herein, we pursue an alternative approach, by placing the CNT catalyst selectively on the horizontal sidewalls of prefabricated TiN electrodes. CNTs were grown across TiN electrodes of 200 nm thickness fabricated on 200 nm oxidised p+ implanted doped silicon substrates. A crosssectional view of these electrodes is outlined in Figure 1a. There is a direct connection between one (Figure 1a) or both electrodes through nickel silicide pads and the Si substrate. For clarity we will denote both electrode configurations as A and B, respectively. In configuration A only one electrode is connected to the substrate whereas configuration B has both connected. One of the electrodes in B can be disconnected after catalyst placement and CNT growth (vida infra) to avoid a competing electrical pathway through the Si substrate. On the top surface of the electrodes an insulating 30 nm thick silicon oxynitride (SiON) hard mask was deposited. These electrode structures are connected within a 4-point probe configuration (Figure 1b). This allows for accurate CNT resistance measurements by eliminating contact resistances and the resistances of the leads.The first challenge in achieving CNTs bridging the electrodes is to deposit metal catalyst on the sidewall of the electrodes. This can be routinely achieved using such methods as physical vapor deposition (PVD) , spincasting (5), and printing (6). However, all these methods lack selectivity and require further steps to isolate the catalyst at specific locations. Electrochemical deposition (ECD) has an intrinsic selective nature in that metal deposition from solution only occurs on conductive surfaces contacted as the ECS Transactions, 18 (1) 845-850 (2009) 10.1149/1.3096544 © The Electrochemical Society 845 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.111.121.42 Downloaded on 2015-06-25 to IP

Selective Actuation of Arrays of Carbon Nanotubes Using Magnetic Resonance

“…The Ni-CNT arrays are grown by CVD from Ni catalyst particles obtained by electrochemical deposition (ECD) on the sidewalls of titanium nitride (TiN) electrodes. − CNTs are grown by CVD underneath the Ni particles that are lifted off from the TiN electrode sidewalls due to the tip growth mode (see Figure b–d), thus remaining horizontally freestanding and loaded with Ni particles at their tips. Scanning electron microscopy (SEM) images of an as-grown Ni-CNT array are presented in Figures a–d.…”

“…A 50 nm thick layer of silicon oxinitride (SiON) is deposited on top of the TiN electrodes in order to prevent CNT growth from the top of the electrodes. More details about the electrode structures, the growth method and the characterization of as-grown carbon nanotubes can be found in refs − . An ECD potential of −3 V, which is applied for 1 s, enables the deposition of high-density (around 10 12 cm –2 ) and quite large (diameter around 100 nm) Ni catalyst particles (see Figure a).…”

Integration of Vertical Carbon Nanotube Bundles for Interconnects

“…In particular, they strengthen the need of carefully designed test structures, processes, and methods to better evaluate the intrinsic electrical properties of the CNT. 21…”

A study of Joule heating-induced breakdown of carbon nanotube interconnects

“…In this work, we investigate the electrothermal behavior of CNT interconnects by comparing their breakdown in air and under high vacuum (10 −5 mbar) conditions. The CNTs are grown by CVD from Ni catalyst particles prepared by electrochemical deposition (ECD) on one of the titanium nitride (TiN) electrodes [33,34]. As-grown CNTs contact the opposing TiN electrode with their outermost shell and can be electrically probed without any need for further post-growth contacting [33,34].…”

“…The CNTs are grown by CVD from Ni catalyst particles prepared by electrochemical deposition (ECD) on one of the titanium nitride (TiN) electrodes [33,34]. As-grown CNTs contact the opposing TiN electrode with their outermost shell and can be electrically probed without any need for further post-growth contacting [33,34].…”