Functionalization of Si3N4 with an 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 on Si3N4 substrates. BAD selectively reacts with NHx (x = 1, 2) terminations on Si3N4 surfaces while showing no affinity toward -OH terminations on 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 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 the inhibitor layer by the 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.