Resistivity increase in ultrafine-line copper conductor for ULSIs

The resistivities of copper (Cu) thin films and damascene Cu fine lines were precisely measured by utilizing Matthiessen's rule. It was shown that this measurement method can produce reliable values without requiring precise and detailed line-dimension measurements. It was found that the increase in resistivities of the fine lines is much more than that of the films, and this increase results in an electron mean free path of 45 nm. We propose a simple equation for expressing line resistivity in terms of both line width and line thickness.