Functionalization of Si3N4 with Aldehyde Inhibitor for Area Selective Deposition of HfO2 and SiO2

Abstract

Area selective atomic layer deposition (AS-ALD) has emerged as a promising strategy to address challenges in 3D nano-structuring of Si devices and the physical limitations of photolithography. Herein, we utilized benzaldehyde (BAD) as an inhibitor to selectively block HfO₂ and SiO₂ ALD thin films. BAD selectively absorbed onto Si₃N₄ surfaces while showing no affinity for SiO₂, leading to selective inhibition of the nitride surface only. BAD effectively blocked HfO₂ ALD using H₂O as the counter reactant up to 1.2 nm thickness, while no blocking was observed on SiO₂ with O₃ due to BAD degradation of BAD by the reactive O₃. To overcome unavoidable degradation, we introduced a cyclic inhibitor exposure AS-ALD process, re-exposing BAD in specific cycles to regenerate the inhibition layer. The chemical interactions between BAD and O₃, particularly BAD oxidation, were investigated experimentally and theoretically using density functional theory (DFT) calculations. The regeneration of inhibitor layer by re-exposure process significantly improved selectivity on SiO₂ even under O₃ conditions. This study provides insights into the fundamental chemical reactions between various inhibitors and counter reactants and offers knowledge applicable to enhancing AS-ALD selectivity for future device fabrication.