Characterization of ion species of silicon oxide films using positive and negative secondary ion mass spectra

Secondary ion species of silicon oxide films have been investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Characterization of thermally grown SiO2 films on silicon has been performed. A diagram showing secondary ion spectra of SiO2 films in both positive and negative polarities indicates the pattern of change in polarities and intensities of ion species from SiO+ to Si5O11−. The ions mostly change from positive to negative polarity between SinO2n−1 and SinO2n. Ion peaks with the strongest intensities in the respective cluster ions correspond to the SinO2n+1 negative ion. Intensities of ion species of SinO2n+2 appear negligibly small. Ion species of Si3O+, Si3O2+ and Si3O3+ have been found at the interface between silicon and SiO2 films. The intensity patterns of these ion species compared to those of SiO2 films indicate that most of these species are not emitted from the SiO2 films, but likely from the SiO structures.