Atomic structure and optical properties of plasma enhanced chemical vapor deposited SiCOH Low-k dielectric film

The SiCOH low-k dielectric film was grown on Si substrate using plasma-enhanced chemical vapor deposition method. Atomic structure and optical properties of the film were studied with the use of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) absorption spectroscopy, Raman spectroscopy, and ellipsometry. Analysis of XPS data showed that the low-k dielectric film consists of Si–O$_4$ bonds (83%) and Si–SiO$_3$ bonds (17%). In FTIR spectra some red-shift of Si–O–Si valence (stretching) vibration mode frequency was observed in the low-k dielectric film compared with the frequency of this mode in thermally grown SiO$_2$ film. The peaks related to absorbance by C–H bonds were observed in FTIR spectrum. According to Raman spectroscopy data, the film contained local Si–Si bonds and also C–C bonds in the $s$–$p^3$ and $s$–$p^2$ hybridized forms. Scanning laser ellipsometry data show that the film is quite homogeneous, homogeneity of thickness is $\sim$2.5%, and homogeneity of refractive index is $\sim$2%. According to the analysis of spectral ellipsometry data, the film is porous (porosity is about 24%) and contains clusters of amorphous carbon ($\sim$ 7%).