Oxidation and Chlorination Reaction Characteristics: A Density Functional Theory Perspective toward the Fundamental Understanding of Etching of Ruthenium and Tantalum Surfaces

Abstract Given the profound industrial relevance of metal surface etching, we performed a detailed density functional theory investigation of the nature of intermolecular interactions between the O2 (and Cl2) etchant(s) and the ruthenium (Ru) (and tantalum (Ta)) surface(s). We assessed the formation energies of the MOx and MClx families of molecular entities (where M denotes Ta or Ru and x spans from 1 to 6), in the gas phase, along with the landscapes of adsorption and desorption energies for Ox/MOx and Clx/MClx on the metal surfaces, to offer valuable insights into the energy profiles required for the fundamental understanding of O2- and Cl2-plasma environments. Our findings unveil that molecular RuO4 may stand out as a prime byproduct for etching the Ru surface when exposed to the O2-plasma, while etching Ru by the Cl2 plasma is much more energetically challenging. Conversely, TaCl3, TaCl4, and TaCl5 may emerge as the predominant etching byproducts for the Ta surface in the Cl2 plasma environment. The climbing image nudged elastic band calculations carried out for analyzing detailed etching reaction paths reveal that the desorption of RuO4 from the Ru surface is a rate-limiting phenomenon, characterized by the formation of a metastable intermediate state [RuRuO4], effectively reducing the energy needed for etching.