We report on the thin film resistivity of several platinum-group metals (Ru, Pd, Ir, and Pt). Platinum-group thin films show comparable or lower resistivities than Cu for film thicknesses below about 5 nm due to a weaker thickness dependence of the resistivity. Based on experimentally determined mean linear distances between grain boundaries as well as ab initio calculations of the electron mean free path, the data for Ru, Ir, and Cu were modeled within the semiclassical Mayadas–Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess the combined contributions of surface and grain boundary scattering to the resistivity. For Ru, the modeling results indicated that surface scattering was strongly dependent on the surrounding material with nearly specular scattering at interfaces with SiO₂ or air but with diffuse scattering at interfaces with TaN. The dependence of the thin film resistivity on the mean free path is also discussed within the Mayadas–Shatzkes model in consideration of the experimental findings.

Ruthenium has emerged as a promising candidate to substitute Cu as the interconnect metallization in future technology nodes. Here, we demonstrate area scaling of Ru wires down to cross-sectional areas of 33 nm² through subtractive patterning by using a metal-spacer patterning technique. The wires were characterized by physical as well as electrical measurements and demonstrate low resistivity, between 20 and $35~\mu \Omega $ cm for cross-sectional areas between 175 and 33 nm².

Co has elicited a strong interest to replace Cu for future interconnect applications in microelectronic circuits due to its potentially lower resistivity and better reliability at scaled dimensions. Here, we demonstrate Co wires with electrical cross-sectional areas as small as 34 nm² using a simple subtractive patterning technique. Semiclassical resistivity modeling of the wire resistivity indicates that grain boundary scattering is the dominant contribution for cross-sectional areas of the order of 100 nm², while the contribution of surface scattering increases drastically below 50 nm². Furthermore, wafer-level reliability tests of the Co wires show the high fusing current densities and a strong resistance to thermoelectric stress demonstrating the potential for robust reliability. The resistivity and the reliability of the Co wires are comparable with those of Ru wires.

Ru has been considered a candidate to replace Cu-based interconnects in VLSI circuits. Here, a methodology is proposed to predict the resistivity of (Ru) interconnects. First, the dependence of the Ru thin film resistivity on the film thickness is modeled by the semiclassical Mayadas-Shatzkes (MS) approach. The fitting parameters thus obtained are then used as input in a modified MS model for nanowires to calculate wire resistivities. Predicted experimental resistivities agreed within about 10%. The results further indicate that grain boundary scattering was the dominant scattering mechanism in scaled Ru interconnects.

We demonstrate 10 nm half-pitch (HP) Ruthenium interconnects filled by atomic layer deposition (ALD). The resistivity and the cross-sectional area of Ruthenium interconnects were determined via the Matthiessen's rule method. We find that the resistivity of Ru was rather independent of the cross-sectional area of the interconnect, increasing from 12 μΩcm for larger lines to 15-17 μΩcm for cross-sectional areas of 200-300 nm ² . 10 nm HP Ru lines showed no electromigration failures at 5 MA/cm ² and 300°C during 1000 hours. Time-dependent dielectric breakdown measurements indicated that Ruthenium does not require a diffusion barrier on both dense and porous low-κ dielectrics.