Reliability and resistance projections for rhodium and iridium interconnects from first-principles

Abstract

We apply first-principles simulations to evaluate several properties related to the resistance and reliability of rhodium and iridium interconnects. We find that both Rh and Ir have significantly higher activation energies of diffusion than state-of-the-art Cu interconnects, suggesting greatly improved resistance to electromigration failure. Since the practical integration of metal interconnects requires an adhesion liner, we calculate the metal-to-metal adhesion, surface scattering characteristics, and via resistance of four potential liner materials: TiN, TiO, TaN, and TaO. We find that TiO gives the strong metal-to-metal adhesion for both Rh and Ir, minimizing the risk of delamination. None of the four liner materials considered are found to have a significant impact on surface scattering of Rh or Ir, while the N-containing liners give lower via resistance than the O-containing liners. This work helps build a better understanding of fundamental material properties related to the practical integration of potential next-generation interconnect metals used for advanced semiconductor technology.

Anisotropic Resistivity Size Effect in Epitaxial Mo(001) and Mo(011) Layers

“…Other elemental metals that are considered for nanoscale conductors include Rh [ 38 , 39 ], Ir [ 40 , 41 ], and Ru [ 42 , 43 , 44 ]. They have 46%, 38%, and 15% smaller ρ o λ products than Mo [ 34 ], respectively, but are challenging due to cost, small earth abundance, and limited process maturity [ 45 , 46 , 47 ].…”

Nucleation and Layer Closure Behavior of Iridium Films Grown Using Atomic Layer Deposition

“…2−6 Additionally, Ir has been considered an alternative conducting material in low-level interconnects such as metal 0 and metal 1, vias, and liners. 7 Although Cu is currently used as the conducting material for the interconnects of integrated circuits, the long electron mean free path (39.9 nm) 8 of Cu drastically increases the resistivity of the Cu layers in state-of-the-art interconnect lines (<10 nm wide). In contrast, Ir has a very short electron mean free path (7.09 nm), 8 a low bulk resistivity (4.7 μΩ cm), and consequently a lower resistivity at the extremely small dimensions of the next-generation semiconductor devices.…”

“…Platinum-group metals, such as Ru, Pt, and Ir, have received significant attention for various applications in microelectronics. Among them, Ir has a high oxidation resistance and a high work function (5.3 eV), compared to that of Ru (4.7 eV), which is advantageous for the suppression of leakage currents of capacitors when used as electrodes in dynamic random-access memory (DRAM) capacitors. − Additionally, Ir has been considered an alternative conducting material in low-level interconnects such as metal 0 and metal 1, vias, and liners . Although Cu is currently used as the conducting material for the interconnects of integrated circuits, the long electron mean free path (39.9 nm) of Cu drastically increases the resistivity of the Cu layers in state-of-the-art interconnect lines (<10 nm wide).…”