Molecular-level insight into amino acid additive effects on ceria-film interactions and STI-CMP selectivity

초록

Amino acids are promising additives in ceria-based slurries for improving STI-CMP selectivity by suppressing Si3N4 removal. However, their physicochemical properties, including charge, hydrophobicity, and molecular structure, can also modify film surface charge and wettability, thereby affecting ceria-film interactions and polishing behavior. This study establishes a framework for understanding how amino acid properties influence film interfacial properties, ceria adhesion, and STI-CMP selectivity. Glycine was used as the model additive, while lysine, glutamic acid, serine, leucine, and proline were selected as representative amino acids with distinct characteristics. Film surface properties were evaluated by zeta potential and contact angle measurements, and ceria-film interactions were characterized by AFM force-distance measurements. Lysine, which exists mainly as a positively charged species at pH 4, strongly adsorbed on SiO2, shifted its zeta potential toward less negative values, weakened ceria-SiO2 attraction, and suppressed SiO2 removal. In contrast, leucine increased the hydrophobicity of Si3N4, enhanced ceria adhesion, and increased Si3N4 removal, lowering selectivity. Proline showed behavior similar to glycine, indicating minimal structural influence under the present conditions. These results provide molecular-level guidance for designing additives to improve STI-CMP selectivity. © 2026 Elsevier B.V.

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