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

We have investigated the surface reaction mechanism during the atomic layer deposition (ALD) of SiO 2 from 3-aminopropyl triethoxysilane (APTES), H 2 O, and O 3 using in situ attenuated total reflection Fourier-transform infrared spectroscopy. After the chemisorption of APTES on the SiO 2 surface, during the H 2 O 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. O 3, in the subsequent cycle, combusts the remaining aminopropyl ligands, possibly producing combustion products such as CO, CO 2, H 2 O, and NO x . 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 O 3 exposure along with the OH groups produced during H 2 O exposure serve as the reactive sites for APTES chemisorption, thus completing the entire ALD cycle.