SiO2 film growth at low temperatures by catalyzed atomic layer deposition in a viscous flow reactor

SiO2 thin films were grown by catalyzed atomic layer deposition (ALD) at low temperatures in a viscous flow reactor using sequential SiCl4 and H2O exposures. Pyridine (C5H5N) was used as a catalyst for both reactant exposures. Micropulsing was employed to avoid possible film contamination by pyridinium chloride. Quartz crystal microbalance experiments measured a SiO2 film growth rate of 1.35 Å per SiCl4/H2O AB cycle at 305 K with SiCl4, H2O and pyridine exposures of 103-104 Langmuir (1 Langmuir = 10− 6 Torr s). This SiO2 ALD growth rate was verified by ex situ X-ray reflectivity, spectroscopic ellipsometry and surface profilometry measurements. The SiO2 ALD film growth rate decreased dramatically at higher temperatures. Transmission Fourier transform infrared spectroscopy studies revealed that the hydrogen-bonded pyridine coverage was correlated with the catalyzed SiO2 ALD growth rates from 305 to 360 K. Larger pyridine pressures were needed for catalyzed SiO2 ALD at higher temperatures to offset the larger pyridine desorption rates. The SiO2 ALD films contained negligible C, N, or Cl impurities as determined by X-ray photoelectron spectrometry. The deposited SiO2 films were also extremely smooth with a surface roughness identical to the initial Si(100) substrate.