Final Report on Alternative Metals for Low-Resistivity Interconnects
Research Report Highlight
This project has successfully (i) calculated the electron mean free path using first-principles calculations, and (ii) employed in-situ transport measurements on epitaxial metal layers to identify the most promising conductive metals to replace Cu.
This 3-year project has successfully (i) developed a method to calculate the electron mean free path using first-principles electronic structure calculations and applied it to the twenty most conductive elemental metals and (ii) employed in situ transport measurements on epitaxial metal layers to experimentally determine the mean free path by fitting the resistivity vs thickness curves for multiple metals. Based on simulations, five metals (Al, Rh, Ir, Ru, Pt) show the potential to have a lower resistivity than Cu for <10 nm interconnects. More metals may be promising if they do not require a liner and/or diffusion barrier layer (as needed for Cu). Experimental measurements agree with the simulation predictions for some metals (Cu, Mo, Ru), show some disagreement (W), or complete disagreement (Ni, Ta, TiN). Thus, more sophisticated non-equilibrium density functional calculations are required to reliably predict the resistivity of narrow metal wires.