Gas-phase surface functionalization of plasma-deposited amorphous silicon and silicon nitride surfaces with aldehydes

We have investigated the surface reactions of 3,5,5-trimethylhexanal (TMH) and pivaldehyde with plasma-deposited amorphous hydrogenated silicon (a-Si:H) and amorphous hydrogenated silicon nitride (a-SiNx:H) surfaces for potential use as inhibitor molecules for area-selective atomic layer deposition (AS-ALD). Surface changes were characterized using in situ attenuated total reflection Fourier transform infrared spectroscopy. We show that, on the a-Si:H surface, TMH and pivaldehyde react with surface –SiHx (x = 1, 2, 3) groups at 150 °C to form alkoxides. At elevated temperatures, the alkoxide formed from pivaldehyde was slightly more thermally stable than that formed after the reaction with TMH. The alkoxide formed after the reaction with pivaldehyde most likely decomposes via the α-hydride elimination reaction because the β-hydride elimination reaction cannot occur, but the alkoxide formed from TMH can decompose via either pathway. Similar to the a-Si:H surface, TMH reacts with surface −SiHx (x = 1, 2, 3) groups on the a-SiNx:H surface at a substrate temperature of 70 °C to form alkoxides. Reaction with −NHx (x = 1, 2) groups on the a-SiNx:H surface led to the formation of aminoalcohols, imines, and enamines. Pivaldehyde also reacts with surface amines but does not form enamines since it does not contain α-hydrogen atoms. Following the adsorption of TMH on the a-SiNx:H surface, upon heating the substrate to 150 °C, desorption of surface species occurs preferentially over the dehydration of aminoalcohols to imines and enamines: this suggests that aldehydes are not ideal inhibitor molecules for AS-ALD with a-SiNx:H as the nongrowth surface.