Surface ligand engineering for defect-suppressed TiO2 dielectrics by functional precursor-assisted ozone ALD

초록

Atomic layer deposition (ALD) enables precise fabrication of metal oxide thin films, but the incomplete removal of precursor ligands can leave residual impurities, limiting the dielectric quality. This study introduced an iodine-containing functional precursor as an intermediate activator between the Ti precursor and oxidant pulses to regulate the surface ligand chemistry and promote ligand removal during the subsequent O3 reaction. Density functional theory calculations indicated that the functional precursor could react with precursor ligands through ligand exchange and beta-hydrogen elimination. After introducing the functional precursor, the TiO2 growth per cycle (GPC) increased from 0.28 to 0.40 & Aring;/cycle. Secondary-ion mass spectrometry confirmed a decrease in the ligand-derived carbon and hydrogen impurities, and X-ray photoelectron spectroscopy showed a decrease in the defect-related oxygen components, indicating the formation of a more stable Ti-O network. These chemical improvements led to a higher film density and lower surface roughness producing a more compact dielectric film. Consequently, the capacitor leakage current decreased, while the dielectric constant increased from 26.0 to 36.3. The process also delivered a step coverage of approximately 95% on a trench structure. This study demonstrated that functional precursor engineering can effectively improve the quality and dielectric performance of a TiO2 film.

키워드