Mechanism of Self-catalytic Atomic Layer Deposition of Silicon Dioxide Using 3-Aminopropyl Triethoxysilane, Water, and Ozone

Abstract

We have investigated the surface reaction mechanism during the atomic layer deposition (ALD) of SiO2 from 3-aminopropyl triethoxysilane (APTES), H2O, and O3 using in situ attenuated total reflection Fourier-transform infrared spectroscopy. After the chemisorption of APTES on the SiO2 surface, during the H2O cycle, the aminopropyl groups in APTES catalyze the hydrolysis of ethoxy ligands, leaving the surface terminated with OH groups—a reaction that would otherwise require an acidic or basic catalyst. O3, in the subsequent cycle, combusts the remaining aminopropyl ligands, possibly producing combustion products such as CO, CO2, H2O, and NOx. Among these products CO reacts with surface OH groups to form monodentate formates and SiH on the surface. The formates and SiH groups produced during O3 exposure along with the OH groups produced during H2O exposure serve as the reactive sites for APTES chemisorption, thus completing the entire ALD cycle.