Mechanistic study of ceria particle redeposition during post-CMP PVA brush cleaning for defect reduction in advanced semiconductor manufacturing

초록

Post-CMP removal of ceria abrasives is critical for defect control, yet residues persist. Using site-tracked cleaning on STI wafers, colloidal AFM, and extended DLVO (XDLVO) analysis, we identify redeposition as the main cause. AFM with ceria probes shows purely repulsive ceria-PVA interactions at pH 11 (no pull-off), while ceria-SiO2 contacts are adhesive. Decomposing approach/retraction curves with XDLVO for the contact between a micron-sized ceria-coated particle and the SiO2 film indicate that, beyond van der Waals, electrostatic double layer, and hydration forces, adhesion is dominated by the formation of a CeOSi bond contributing ∼10 nN at detachment. Adhesion decreases with rising pH, consistent with strengthened EDL and hydration repulsion. Additives modulate this bonding: 0.5–2 mM oxalic acid passivates surface Ce3+ and nearly eliminates adhesion at 2 mM, whereas glycine fails to reduce adhesion and can raise it to ∼11–14 nN via additional hydrogen bonding to silanols. Thus, particles lifted by the PVA brush are readily released but reattach to SiO2, making redeposition the governing failure mode. The mechanism links nanoscale forces to wafer outcomes and suggests design rules: maximize initial removal forces and suppress CeOSi formation with carboxylates to prevent reattachment, reducing residues and improving yield. © 2026 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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