Hydrogen bond-mediated activation of HF in SiO2 thermal dry etching: A first-principles study of catalytic additives

Thermal dry etching of SiO2 is essential for advanced semiconductor manufacturing, yet the role of additives in modulating hydrogen fluoride (HF) reactivity remains unclear. Using density functional theory, we show that HF⋯additive complexes, rather than ionized species such as F− or HF2−, act as effective etching agents. Hydrogen bonding with additives activates HF through stabilization, polarization, and bond weakening, thereby facilitating the reaction on the SiO2 surface. N-based and O-based additives with different functional groups (H2O, phenol, isopropyl alcohol, aniline, pyridine, dimethylamine, and trimethylamine) were evaluated, and the activation trends reveal that N-based additives enhance HF activation to a greater extent than O-based additives, and π-conjugation in aromatic systems diminishes lone pair availability and weakens activation. These electronic effects are directly mirrored in the catalytic etching pathways and energetics: stronger lone pair donation results in lower barriers, whereas delocalization suppresses the catalytic effect. Together, these results identify lone pair character and electron delocalization as fundamental determinants of additive-controlled reactivity, providing a transferable framework for SiO2 thermal dry etching process development.