Topic Name: Using Nanotubes in Computer Chips : A new technique for growing carbon nanotubes should be easier to integrate with existing semiconductor manufacturing processes
Research persons: Carl V. Thompson
Location: Cambridge, United States
Source: "Low Temperature Synthesis of Vertically Aligned
Carbon Nanotubes with Electrical Contact to Metallic Substrates Enabled by
Thermal Decomposition of the Carbon Feedstock," Gilbert Nessim, Carl V. Thompson
et al, Nano Letters, Aug. 31, 2009
Results: Researchers in the lab of MIT materials science
professor Carl V. Thompson grew dense forests of crystalline carbon nanotubes on
a metal surface at temperatures close to those characteristic of computer chip
manufacturing. Unlike previous attempts to do the same thing, the researchers'
technique relies entirely on processes already common in the semiconductor
industry. The researchers also showed that the crucial step in their procedure
was to preheat the hydrocarbon gas from which the nanotubes form, before
exposing the metal surface to it.
Why it matters: The transistors in computer chips are
traditionally connected by tiny copper wires. But as chip circuitry shrinks and
the wires become thinner, their conductivity suffers and they become more likely
to fail. A simple enough manufacturing process could enable carbon nanotubes to
replace the vertical wires in chips, permitting denser packing of circuits.
How they did it: In a vacuum chamber, the researchers
vaporized the metals tantalum and iron, which settled in layers on a silicon
wafer. Then they placed the coated wafer at one end of a quartz tube, which was
inserted into a furnace. At the wafer's end of the tube, the furnace temperature
was 475 degrees C; but at the opposite end, the temperature varied. The
researchers pumped ethylene gas into the tube from the end opposite the wafer.
When the temperature at that end approached 800 degrees, the ethylene
decomposed, and the iron on the wafer catalyzed the formation of carbon
Next steps: The researchers are trying to determine whether
different combinations of metals and hydrocarbon gases can lower the catalytic
temperature even further and improve the quality of the nanotubes.
Funding: The research was sponsored by the MARCO
Interconnect Focus Center and partially by Intel (Gilbert Nessim, who was a
graduate student in Thompson's lab, was supported by an Intel Fellowship).
About The Researcher :
Carl V. Thompson
Stavros Salapatas Professor of Materials Science and Engineering
Professor Thompson received his SB in Materials Science and Engineering from
the Massachusetts Institute of Technology in
l976. He received his SM and PhD degrees in applied physics from Harvard
University in 1977 and 1982 respectively. He was an IBM postdoctoral fellow in
the Research Laboratory of Electronics at
MIT in l982 and joined the faculty of the
Department of Materials Science and Engineering in l983. He received an IBM
faculty development award in l983 and was appointed the Mitsui career
development assistant professor of contemporary technology in l984 and l985. In
1987 he was appointed associate professor of electronic materials, and became a
full professor in 1992. He is currently the Stavros Salapatas Professor of
Materials Science & Engineering and Director of the
Materials Processing Center
Professor Thompson spent the 1990-91 academic year at the University of
Cambridge Department of Materials Science and Metallurgy, where he was awarded a
United Kingdom Science and Engineering Research Council Visiting Fellowship. He
spent the 1997-98 academic year at the Max-Plank Institute fur Metallforschung
in Stuttgart and received a research award for Senior U.S. Scientist from the
Alexander Von Humboldt Foundation. Professor Thompson's research is carried out
in affiliation with the MIT Microsystems
Technology Laboratory and the MIT
Materials Processing Center, as well as the Department of Materials Science
and Engineering. In 1999, Prof. Thompson was named an SMA Fellow in the
Singapore-MIT Alliance Program and
Co-Chairs the SMA program in Advanced Materials for Micro and Nano-Systems.
Professor Thompson has served on the Materials
Research Society (MRS) Council, was the second Vice-President in 1994, the
first Vice-President in 1995, and the President in 1996. He continues to serve
on several committees and has organized a number of MRS symposia. He co-chaired
the Spring 1991 MRS meeting.
Professor Thompson worked briefly for U.S. Steel and General Electric and has
been a consultant for a number of microelectronics companies, new companies
exploiting nanotechnology, and legal firms. Professor Thompson has also taught
short courses at a number of companies, including Hewlett-Packard, Chartered
Semiconductor, and Digital Equipment Corporation.
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