On the use of alloying elements for Cu interconnect applications

Abstract

To address the future use of alloying elements for Cu interconnect applications in integrated circuits, first, available bulk experimental data such as residual resistivity per at. % solute and binary phase diagrams are used to arrive at a set of 24 potential elements. Next, experimental results in thin films and lines allow the authors to arrive at a smaller set that includes ten elements, namely, Pd, Au, Al, Ag, Nb, Cr, B, Ti, In, and Mn, with higher priority and six, namely, Zn, V, C, Mg, P, and Sn with lower priority for further studies. These additional studies are needed before a strong case for or against alloying additions to Cu can be made. The available thin film and line data are summarized in a series of tables that should prove useful for the readers. In particular, the thin film data allow the authors to obtain an effective average residual resistivity (EARR) per at. % solute that combines the effects of impurity scattering, second phase precipitates, and grain size refinement resulting from solute additions.