Structural Analysis for Water Absorption of SiOF Films Prepared by High-Density-Plasma Chemical Vapor Deposition

Fluorine-doped silicon oxide (SiOF) films, prepared by high-density-plasma chemical vapor deposition, are investigated as to the effect of bond structure on water absorption. In this investigation, two kinds of SiOF films, containing 12% and 8% fluorine atoms, were compared with regard to the change in their bond structure before and after accelerated water absorption. Fourier transform infrared (FT-IR) spectra, thermal desorption mass spectroscopy (TDS) spectra and Raman spectra studies clarified the following. (1) The SiOF film which contains 12% fluorine atoms has more Si–F bonds than that containing 8% fluorine atoms, but it has fewer 3-fold rings. (2) The SiOF film which contains 8% fluorine atoms absorbs little water, and its Si–F bond does not change after water absorption. (3) The 3-fold ring of the SiOF film which contains 12% fluorine atoms has an unstable F–Si–O–Si bond structure. (4) The F–Si–O–Si bond structure of the 3-fold ring is easily changed to the F–Si–OH and Si–OH bond structures due to hydration, upon water absorption.