Spectral Characterization of Amorphous Fluorinated Carbon Film with a Low Dielectric Constant

Amorphous fluorinated carbon films have been prepared from the gaseous mixture of CH4 and C4F8 by plasma enhanced chemical vapor deposition (PECVD) method. The dielectric constant of the deposited film under the experimental conditions is 2.3. Fourier transform infrared spectrum (FTIR) indicates that the film contains minor unsaturated double bonds such as C=O, C=C , etc in addition to CFn (n = 1-3) configurations. However, no sign reveals the existence of C-H and O-H in the film. Further, X-ray photoelectron spectrum (XPS) verifies that carbon in the deposited film has six chemical states, which are CF3 (8%), CF2 (19%), CF (26.7%), C-CFn (42.5%), C-C(3.3%) and C=O (0.5%). It indicates that about 54% of carbon atoms in the film bond with fluorine atoms, and around 43% bond with carbon atoms of CFn configurations instead of bonding directly with fluorine atoms. The adjacent carbon atoms without bonding with fluorine are very less.