Transcript Interconnect Focus Center

SEMICONDUCTOR
SUPPLIERS
Goal: Fabricate and perform electrical tests on
various interconnected networks of nanotubes in two
dimension and three dimension.
Carbon Nanotube Interconnects
Challenge: Design compatible processes to
integrate nanotube structures into present and
future interconnect architectures
Nanotube Interconnects (Demonstrated Abilities)
* Ultra-small Dimensions (~1 nm diameter)
* Near Defect Free, Robust Structure
* High Current Densities (~109 Amps/cm2)
* Negligible Electromigration
* Ballistic/Quasi-ballistic Electron Transport
* Growth in 2-D, 3-D Architectures
* Junctions between Individual Nanotubes
* Measurement of Ballistic Transport in Nanotubes
External Collaborations: SUNY Albany, Georgia
Institute of Technology, Army Research
Laboratory, Intel Corporation, NTT Japan,
Chinese Academy of Sciences
2 mm
Singlewalled Nanotube Networks
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Nanotube Interconnects: Several properties of nanotubes have been
demonstrated (including ballistic eletron transport, high current carrying
capacity, low electrmigration, high thermal conductivity etc,. Which makes
nanotubes excellent material for interconnects. The challenge however is to
develop nanotube based architectures with control, with nanotube-nanotube
and nanotube-metal junctions and test their electrical properties and finally
to interface them with micron and sub-micron scale VLSI architectures.
There is also a need to develop compatible synthesis procedures that will
allow the integration of nanotube based circuits into Si based or an all
carbon based chip design and fabrication. A second goal is to create micro
scale nanotube based architectures for on-chip thermal management.
Acoomplishments: Our most accomplishedresults relate to the growth of
nanotube architectures. We have designed and fabricated nanotube
interconnect architectures using a substrate selective (SiO2 over Si) CVD
growth process that involves a one step vapor phase catalyst delivery
deposition process, different architectures (vertically and horizontally
aligned simultaneously) of multiwalled nanotube arrays can be fabricated
over substrate patterns. We have also fabricated organized networks of
singlwewalled nanotubes over lithographically fabricated Si substrates. The
density of these networks can be controlled and these can be fabricated over
large (macroscopic) areas. We have also made singlewalled nanotube
junctions by electron beam welding of two crossed individualo nanotubes.
Such junctions will be important in future interconnect architectures.
Various structures of hierarchically branched nanotube structures have also
been controlled made using porous alumina oxide templates as molds. We
have also done extensive electrical transport measurements on individual
and multiple nanotube interconnect structures to test their high current
carrying capacity and electromigration stability.
Select Five Key Publications
1.
B. Q. Wei, R. Vajtai and P. M. Ajayan, “Reliability
and current carrying capacity of carbon nanotubes“,
Appl. Phys. Lett., 79, 1172 (2001).
2.
B. Q. Wei, R. Vajtai, Y. Jung, J. Ward, Y. Zhang, G.
Ramanath and P. M. Ajayan, “Organized assembly
of carbon nanotubes ”, Nature, 416, 495 (2002).
3.
M. Terrones, F. Banhart, N. Grobert, J.-C. Charlier,
H. Terrones, and P.M. Ajayan, "Molecular Junctions
by Joining Single-Walled Carbon Nanotubes",
Phys. Rev. Letters, 89, 075505 (2002).
4.
Y. J. Jung, Y. Homma, R. Vajtai, Y. Kobayashi, T.
Ogino and P. M. Ajayan, “Straightening suspended
single walled carbon nanotubes by ion irradiation“,
Nanoletters, 4, 1109 (2004).
5.
S. K. Biswas, L. J. Schowalter, Y. J. Jung, A.
Vijayaraghavan, P. M. Ajayan and R. Vajtai, “Room
temperature resonant tunneling of electrons in
carbon nanotube junction quantum wells“, Appl.
Phys. Lett., 86, 183101 (2005).
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b
Horizontal Multiwalled CNT Interconnects
100 mm
c
Singlewalled
CNT
Junctions
Vertical Multiwalled
CNT Interconnects
d
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• Controlled MWNTs synthesized inside porous anodic
aluminum oxide (AAO) templates using various
synthesis parameters
• SEM images above show MWNTs with different
numbers of graphene walls, controllably fabricated
inside the nano-channels of the AAO templates.
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Fabrication of High-throughput Single- AFM phase image of (a) single NT bundle connecting two
Walled Carbon Nanotube–Metal
gold pads (11x11µm2) and (b) Y junction SWNT bundle
Interconnect Structures
crossing between metal pads (15x15µm2)
(a)
(b)
2.5 nm
SWNTs seen between Ti/Au (20/200 nm thick) electrodes on a
highly doped silicon substrate with 1000 Å thermally grown oxide.
The device width between electrodes (gap) is 7.5 µm, and the
electrodes are 100 µm in width running the length of the sample
(~15 mm).
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We studied the effect of low energy electron irradiation on
the electrical conductivity of individual singlewalled
nanotubes contacted by e-beam lithography. Conductivity
of the SWNT interconnect was measured in-situ using
electrical probes mounted inside an SEM.
Conductivity is found to decrease as exposure dose
increased and the band-gap of the structure
increased as exposure dose increased
Top: Schematic of nanotube interconnect in
its test configuration. Bottom: Variation of
conductivity with electron dose
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