Two-Step Ar/N₂ Plasma Treatment on SiO₂ Surface for Cu/SiO₂ Hybrid Bonding

A surface pre-treatment is a critical process in low temperature Cu/SiO 2 hybrid bonding, significantly improving the quality of bond for both the Cu-Cu and SiO 2 -SiO 2 interfaces. Previously, we demonstrated that a two-step Ar/N 2 plasma treatment could effectively enhance both the quality of Cu-Cu bonding and the antioxidative properties of copper surfaces through copper nitridation. In this study, we investigated the effects of a two-step Ar/N 2 plasma treatment on a SiO 2 surface for application to Cu/SiO 2 hybrid bonding. The chemical states of a SiO 2 surface were measured using XPS (X-ray photoelectron spectroscopy) after the two-step Ar/N 2 plasma treatment, indicating that the SiO 2 surface reacted with the N 2 plasma and led to the substitution of oxygen in the Si-O bonds with nitrogen and the formation of three distinct entities, -N(-Si) 2 , N+(-Si) 2 , and N(-Si) 3 . After SiO 2 -SiO 2 bonding, Si nanocrystals were exclusively observed at the bonding interface in the two-step Ar/N 2 plasma treated specimen, in contrast to non-plasma treated specimen, as indicated by a TEM (Transmission Electron Microscope) analysis. Shear tests were conducted to assess the bonding strength of SiO 2 -SiO 2 , revealing that the specimens treated with the two-step Ar/N 2 plasma process exhibited on average double the shear strength compared to non-plasma treated specimens.