Mechanisms of SiO2 film deposition from tetramethylcyclotetrasiloxane, dimethyldimethoxysilane, and trimethylsilane plasmas

The deposition of SiO2 films from alkoxysilane/O2 and alkoxysilane/N2O plasmas has been investigated using 1, 3, 5, 7-tetramethylcyclotetrasiloxane, dimethyldimethoxysilane, and trimethylsilane as Si precursors. Films were analyzed using Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, spectroscopic ellipsometry, and scanning electron microscopy. Film deposition rates and hydrocarbon incorporation in the SiO2 films decrease with addition of O2 or N2O. High-quality SiO2 films are deposited at high oxidant concentrations with all three precursors. The effects of applied rf plasma power, substrate temperature, and substrate position in the reactor on film quality and deposition rate were also examined. Negative apparent activation energies for film deposition have been observed, suggesting a deposition process dominated by surface adsorption/desorption reactions. Gas phase species in these plasmas were studied with optical emission spectroscopy and mass spectrometry and are correlated with film deposition. For films deposited from low oxidant-containing plasmas, post deposition treatment with an O2 plasma serves to remove hydrocarbon contamination.