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–O4 bonds (83%) and Si–SiO3 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 SiO2 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–p3 and s–p2 hybridized forms. Scanning laser ellipsometry data show that the film is quite homogeneous, homogeneity of thickness is ~2.5%, and homogeneity of refractive index is ~2%. According to the analysis of spectral ellipsometry data, the film is porous (porosity is about 24%) and contains clusters of amorphous carbon (~7%).