Pyridine-Catalyzed Atomic Layer Deposition of SiO₂ from Hexachlorodisilane and Water: An In Situ Mechanistic Study

Pyridine-catalyzed atomic layer deposition (ALD) of SiO₂ from hexachlorodisilane and water was studied by in situ analyses using Fourier-transform infrared spectrometry and a quartz crystal microbalance. Although it has been observed that ALD SiO₂ can grow even when only one half-reaction is catalyzed, typical self-limiting growth of SiO₂ by catalytic ALD has been achieved when both half-reactions are catalyzed by pyridine. The in situ analyses revealed that the unexpected growth of SiO₂, when only one half-reaction was catalyzed, was caused by the presence of residual pyridine that had not yet desorbed from the previous half-reaction. The retardation of catalyst desorption was more prominent on the OH-terminated SiO₂ surface than on the Cl-terminated surface, which is related to the significantly higher desorption energy of pyridine species on the hydroxyl surface calculated using density functional theory.