Atomic Layer Modulation of Ruthenium Aluminum Oxide through Reactivity Control of Precursors for Seedless Copper Interconnects

Abstract

We fabricated the RuAlO x multicomponent thin film by using atomic layer modulation (ALM) based on precursor chemical reactivities and steric hindrance effects. Dicarbonyl-bis(5-methyl-2,4-hexanediketonato)Ru(II) (Carish) and dimethylaluminum isopropoxide (DMAI) were employed as Ru and Al precursors, respectively, with H2O as the counter reactant. Theoretical calculations based on machine learning interatomic potential were performed to investigate the surface chemical reactions of the precursors and the feasibility of the ALM concept to modulate RuAlO x films. The transmission electron microscopy analysis revealed a distinctive structure of the RuAlO x thin films, where the typical columnar growth of Ru was prevented by the surrounding amorphous Al2O3. Sheet resistance measurement results and X-ray diffraction analyses confirmed that a 50 nm Cu/5 nm RuAlO x /SiO2 structure remained stable even after annealing at 600 degrees C for 30 min, without any Cu silicide formation. These results suggest that a 5 nm RuAlO x thin film effectively prevents the diffusion of 50 nm of Cu. We believe that RuAlO x ALM thin films can be used as diffusion barriers against Cu, with improved performance compared to that of films with the typical Ru columnar grain structure.