Functionalization of the SiO₂ Surface with Aminosilanes to Enable Area-Selective Atomic Layer Deposition of Al₂O₃

Small-molecule inhibitors are promising for achieving area-selective atomic layer deposition (ALD) due to their excellent compatibility with industrial processes. In this work, we report on growth inhibition during ALD of Al₂O₃ on a SiO₂ surface functionalized with small-molecule aminosilane inhibitors. The SiO₂ surface was prefunctionalized with bis(dimethylamino)dimethylsilane (BDMADMS) and (N,N-dimethylamino)trimethylsilane (DMATMS) through solution and the vapor phase. ALD of Al₂O₃ using dimethylaluminum isopropoxide (DMAI) and H₂O was performed on these functionalized SiO₂ surfaces. Our in situ four-wavelength ellipsometry measurements show superior growth inhibition when using BDMADMS and DMATMS in sequence over just using BDMADMS or DMATMS. Vapor phase functionalization provided a growth delay of ∼30 ALD cycles, which was similar to solution-based functionalization. Using in situ attenuated total reflection Fourier transform infrared spectroscopy, we show that the interaction of DMAI with SiO₂ surfaces leads to pronounced changes in absorbance for the Si-O-Si phonon mode without any detectable DMAI absorbed on the SiO₂ surface. Detailed analysis of the infrared spectra revealed that the decrease in absorbance was likely caused by the coordination of Al in DMAI to O atoms in surface Si-O-Si bonds without the breaking the Si-O-Si bonds. Finally, we postulate that a minimal amount of DMAI remains adsorbed on surface Si-O-Si bonds even after purging, which can initiate ALD of Al₂O₃ on functionalized SiO₂: this highlights the need for higher surface coverage for enhanced steric blocking.