Resistivity Size Effect in Encapsulated Cu Thin Films

The work addresses the resistivity increase in Cu interconnects with decreasing linewidth. The surface and grain boundary scattering parameters in Cu thin films encapsulated in SiO2 with and without Ta barrier layers are quantified, and grain boundary scattering is shown to be much greater than surface scattering. 21 samples and 17,882 Cu grains were measured to provide the grain size data. This work indicates that significant mitigation of the Cu resistivity increase with decreasing linewidth is possible, if the grain size can be maintained larger than the electron mean free path (39 nm at room temperature).