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.
Microelectronics Reliability