Simultaneous Formation of Multiwall Carbon Nanotubes and their End-Bonded Ohmic Contacts to Ti Electrodes for Future ULSI Interconnects

Abstract

We have succeeded in growing multiwall carbon nanotubes (MWNTs) with low-resistance ohmic contacts to titanium electrodes by hot-filament chemical vapor deposition (HF-CVD) using a nickel catalyst layer on a titanium electrode. The contact resistance of the sample with nickel/titanium electrodes was two orders of magnitude smaller than that of the sample with nickel catalyst electrodes without titanium. We assumed that the low-resistance ohmic contact was achieved by forming titanium carbide (TiC) during the growth at the MWNT/titanium electrode interface. Moreover, we have demonstrated the growth of vertically aligned bundles of MWNTs, which were end-bonded to the lower titanium electrodes, selectively in via holes. We believe this is the first report of such simultaneous formation of MWNTs and their end-bonded low-resistance ohmic contacts, and its first trial application to carbon nanotube (CNT) vias for future ULSI interconnects.

Selective Growth of Carbon Nanotubes using Two-step Etch Scheme for Semiconductor Via Interconnects

“…A Ti contact layer (1 nm), a Co catalyst layer (3 nm) and a silicon nitride (Si 3 N 4 ) etch stopper layer (20 nm) are deposited sequentially on the TiN layer. A Ti contact layer forms conducting TiC ohmic layer leading to ohmic contact between CNTs and TiN BE [14]. Photolithography and a plasma etch process were used for BE patterning.…”

“…With such properties it has been investigated as a candidate for vertical interconnects competing with copper in nano-scale feature sizes in semiconductor industry [6][7][8][9][10]. Although the integration of CNT interconnects has been tried by many other groups [8][9][10][11], most groups have used e-beam evaporation for the catalyst material or lift-off method for the catalyst pattern which are not compatible with current semiconductor processes. Compatibility with pre-existing technologies would be an important guideline for the introduction of CNT to the semiconductor industry.…”

Carbon Nanotube as a VLSI Interconnect

“…A different approach is etching via down to metal 1 layer and growing the CNTs in these vias [19,21]. In [21] dry etching stops at a film of the catalyst (Ni or Co). Arrays of MWCNTs are formed by hot-filament CVD (HF-CVD).…”

Low Temperature Growth of Single-Walled Carbon Nanotubes from Pt Catalysts under Low Ethanol Pressure by Alcohol Gas Source Method

“…Single-walled carbon nanotubes (SWNTs) have attracted great interest for nanometer-scale devices, such as field effect transistor (FET) [1,2] and LSI interconnects [3,4]. Among a lot of methods for SWNTs growth, catalytic chemical vapor deposition (CVD) has several advantages such as high yield production, low growth temperature, and good controllability of SWNT position and diameter.…”