First-Principles Evaluation of fcc Ruthenium for its use in Advanced Interconnects

Abstract

As the semiconductor industry turns to alternate conductors to replace Cu for future interconnect nodes, much attention has been focused on evaluating the electrical performance of Ru. The typical hexagonal close-packed (hcp) phase has been extensively studied, but relatively little attention has been paid to the face-centered cubic (fcc) phase, which has been shown to nucleate in confined structures and may be present in tight-pitch interconnects. Using ab initio techniques, we benchmark the performance of fcc Ru. We find that the phonon-limited bulk resistivity of the fcc Ru is less than half of that of hcp Ru, a feature we trace back to the stronger electron-phonon coupling elements in hcp Ru that are geometrically inherited from the modified Fermi surface shape of the fcc crystal. Despite this benefit of the fcc phase, high grain boundary scattering results in increased resistivity compared to Cu-based interconnects with similar average grain size. We find, however, that the line resistance of fcc Ru is lower than that of Cu below 21 nm line width due to the conductor volume lost to adhesion and wetting liners. In addition to studying bulk transport properties, we evaluate the performance of adhesion liners for fcc Ru. We find that it is energetically more favorable for fcc Ru to bind directly to silicon dioxide than through conventional adhesion liners such as TaN and TiN. In the case that a thin liner is necessary for the Ru deposition technique, we find that the vertical resistance penalty of a liner for fcc Ru can be up to eight times lower than that calculated for conventional liners used for Cu interconnects. Our calculations, therefore, suggest that the formation of the fcc phase of Ru may be a beneficial for advanced, low-resistance interconnects. arXiv:2001.02216v3 [cond-mat.mtrl-sci] a) fcc b) hcp

Mechanisms of Scaling Effect for Emerging Nanoscale Interconnect Materials

“…Simplifications must be made to make this approach practical. For example, normalized full-band relaxation time approximation for the linearized Boltzmann transport equation (BTE) [ 19 ] is used to derive the scattering rate in a density-functional-theory (DFT) calculation for metal resistivity [ 20 ]. First-principles predictions can be used to determine the product of the bulk resistivity times the bulk electron mean-free-path without calculating the electron scattering explicitly [ 21 , 22 ].…”

Prediction of Co and Ru Nanocluster Morphology on 2D MoS2 from Interaction Energies

“…In the present study, we will expand the knowledge gained from our previous work on Cu on MoS 2 and apply it to the adsorption of small Co n and Ru n clusters on an MoS 2 ML, where n = 1 -4. Co and Ru are of great interest in conjunction with MoS 2 for application in advanced interconnects as alternatives to Cu [30,31,32,33,34,35] and TaN. Applications in catalysis include Pt-free hydrogen evolution catalysts.…”

Prediction of Co and Ru nanocluster morphology on 2D MoS2 from interaction energies

“…In the present study, we will expand the knowledge gained from our previous work on Cu on MoS 2 and apply it to the adsorption of small Co n and Ru n clusters on an MoS 2 ML, where n = 1-4. Co and Ru are of great interest in conjunction with MoS 2 for application in advanced interconnects as alternatives to Cu [30][31][32][33][34][35] and TaN. Applications in catalysis include Pt-free hydrogen evolution catalysts [36][37][38][39][40][41].…”