Enhanced Ruthenium Removal and Superior Surface Quality via Abrasive-Free Chemical Mechanical Polishing Using Synergistic Catalysis with the H2O2/PDS/FeIII-NTA System

Abstract

As the feature sizes of integrated circuits continue to shrink, the phenomenon of electrical migration in Cu interconnects becomes more severe. Due to the excellent properties of Ru such as short electron mean free path and good resistance to electrical migration, it has the potential to become the next-generation interconnect material. Ru chemical mechanical polishing (CMP) is a crucial step in the fabrication of integrated circuits, with oxidation being the step limiting the Ru removal rate, which affects the efficiency of semiconductor manufacturing. In this study, using the H₂O₂/PDS/Fe^III-NTA system, the removal rate of Ru is improved to 1202 Å min⁻¹ via abrasive-free CMP at pH = 7; the surface roughness is only 0.94 nm, demonstrating superior surface quality at the atomic level. This system features a synergistic catalytic mechanism, producing the active oxidants HO^•, SO₄^•−, and Fe^IV = O. These active oxidants have strong oxidation capacity and lead to the oxidation of Ru into RuO₂ and RuO₃ and their subsequent oxidation into soluble RuO₄⁻ and RuO₄²⁻, which results in the formation of a porous oxide layer on the surface of Ru. The oxidation and mechanical effects reach an equilibrium state and accelerate the removal of Ru.