A Comparison of Electromigration in Bulk and Thin - Film Aluminum

Abstract

AbstractThe dominant mode of electromigration in polycrystalline Al thin - film conductors is along grain boundaries when the conductor width is significantly larger than the grain size. Integrated circuit feature sizes, however, have now decreased to the point where microstructures are no longer polycrystalline, but are near - bamboo. Electromigration must operate along pathways other than grain boundaries in the bamboo segments. Here drift velocity data is presented for bamboo microstructures with widths down to 0.6 μm and compared with drift data available in the literature for thin films with a variety of microstructures and bulk Al. Bamboo films show lower drift velocities and higher activation energies for drift than polycrystalline films. The data for bamboo microstructures is consistent with drift measurements performed on bulk Al indicating that the transport mechanism in bamboo films is identical to that in bulk Al.