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

초록

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.

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