Environmentally friendly post-CMP cleaning of ceria nanoparticles with different structures and surface activities

The surface activity of ceria nanoparticles (NPs), defined by the Ce³⁺/Ce⁴⁺ ratio, plays a critical role in determining the silicon oxide removal rate during chemical mechanical planarization (CMP). While a higher Ce³⁺ content promotes Ce–O–Si bond formation for effective oxide removal, these strong bonds hinder residual particle removal during post-CMP cleaning, often requiring hazardous diluted hydrofluoric acid (DHF). In this study, we propose two environmentally benign alternatives—etidronic acid (EA)–H₂O₂ and KOH solutions—and evaluate their cleaning efficiency against conventional DHF. Using nanoclustered (NC)- and cubic fluorite (CF)-structured ceria NPs, we demonstrate that NC-ceria enables more effective post-CMP cleaning due to its enhanced surface activity. Both EA–H₂O₂ and KOH solutions achieve comparable cleaning performance to DHF solution while minimizing substrate damage. These findings highlight the importance of ceria surface chemistry and offer a sustainable route to improve post-CMP cleaning in precision semiconductor manufacturing.