Room-temperature deposition of high-purity silicon oxide films by RF plasma-enhanced CVD

High-purity silicon oxide films have been deposited at near room temperature by remote-type RF plasma-enhanced CVD using a mixture of tetramethoxysilane and oxygen. The effects of the partial pressure ratio of oxygen, RF power, total pressure and substrate position on film composition were studied. The chemical composition and bonding state of the films deposited were evaluated with Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy, and the film surface was observed by atomic force microscopy. It was found that the amount of carbon impurities in deposited films arising from the source material could be reduced by increasing the oxygen partial pressure ratio. The absorption bands due to hydroxyl groups became markedly smaller when either the RF power was increased from 100 to 500 W or the distance between the center of the coil and the substrate was decreased from 400 to 200 mm. Films deposited under the optimal conditions contained no SiCH3, SiOCH3, SiOH or SiH bonds, and the compositional quality was very close to that of films obtained by thermal oxidation.