Tailoring surface chemistry for area-selective HfO2 films: Experimental and DFT insights

초록

Area-selective atomic layer deposition (AS-ALD) of HfO2 provides a promising bottom-up route for nextgeneration nanoelectronic device fabrication by enabling precise material placement without the need for conventional lithography. In this work, we demonstrate a combined experimental and theoretical approach to achieve robust AS-ALD of HfO2 on SiO2 surfaces, while suppressing film growth on SiN and Pt substrates. Diluted HF pretreatment of SiO2 (0.5 wt%) creates abundant surface hydroxyl groups that promote strong interaction with the Hf precursor (tetrakis(ethylmethylamino)hafnium, TEMAH) and rapid nucleation, whereas higher kinetic barriers on SiN and Pt lead to significantly delayed film formation. By periodically integrating HF etches into the ALD sequence ("ALD-etch supercycle"), HfO2 nuclei on the non-growth areas are removed, thus preserving high deposition selectivity over many cycles. Density functional theory (DFT) calculations confirm that the observed surface-dependent selectivity originates from differences in activation energies for precursor adsorption. Furthermore, the HfO2 thin films grown at elevated temperatures (e.g., 250 degrees C) exhibit nearstoichiometric composition, minimal carbon incorporation, and reduced suboxide defects, as validated by indepth X-ray photoelectron spectroscopy (XPS) analysis. This inherently selective ALD strategy, combining substrate functionalization, supercycle etch steps, and optimized temperature windows, offers a powerful solution for advanced patterning and self-aligned processes in future semiconductor manufacturing.

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