As
nanoscale circuits continue to shrink, electrical
resistivity increases in the wiring and limits the
maximum circuit speed. A new simulation program developed
by researchers at the National Institute of Standards
and Technology (NIST) and George Washington University
(GWU) can be used to predict such increases with
greater input flexibility and model accuracy than
other methods. The software program is expected to
help the semiconductor industry design and test devices
more efficiently and with greater cost-effectiveness.
On average, an electron can travel only 39 nanometers
in pure, bulk copper at room temperature before it
is scattered by thermal vibrations of the copper
atoms. But, as the dimensions of the wiring shrink,
additional scattering by surfaces and grain boundaries
within the metal lead to undesirable increases in
resistivity. The NIST/GWU computer program, described
in a recent paper in Microelectronics Reliability,*
enables users to examine how these additional mechanisms
alter the resistivity of the thin, narrow metal lines
that make up the circuit wiring.
As described in the journal article, NIST researchers
used the simulation program to demonstrate that,
at critical nanoscale dimensions, electron scattering
from surfaces and grain boundaries have effects that
are interdependent. This interdependence could not
be predicted using methods previously available.
The finding has implications for both achievable
circuit speed and electrical measurements of the
dimensions of thin, narrow lines.
For information about obtaining the software code
and a forthcoming NIST technical report on the project,
contact Richard Allen at (301) 975-5026 or richard.allen@nist.gov .
* A.E. Yarimbiyik, H.A. Schafft, R.A. Allen, M.E.
Zaghloul, D.L. Blackburn. 2005. Modeling and simulation
of resistivity of nanometer scale copper. Microelectronics
Reliability. Posted online Dec.19.
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