Structure characterization of carbon and fluorine-doped silicon oxide films with low dielectric constant

Abstract

Abstract Carbon and fluorine-doped silicon oxide (SiO 2 :C,F) films with low dielectric constant have been deposited from tetraethoxysilane (TEOS), C 4 F 8 and Ar using plasma enhanced chemical vapor deposition (PECVD) method. X-ray diffraction (XRD) analysis shows that SiO 2 :C,F film is amorphous. Fourier transform infrared (FTIR) spectra illustrate that the intense absorption band between l000 and 1300 cm −1 becomes broader with increasing C 4 F 8 flow rate which indicates that the amount of fluorocarbon compound incorporated into the film increases. C 1s X-ray photoelectron spectrum reveals that the fluorocarbon compound has a high degree of cross-linked structure because of the existence of only C–F bonds. By fitting the absorption band of Si–F n at about 940 cm −1 and Si 2p X-ray photoelectron spectrum using Gaussian profile, we can consider that there are (O–) 2 Si(–F) 2 and (O–) 3 Si–F groups in the deposited films, and the former is less than the latter. The measurements of capacitance–voltage ( C – V ) characteristics of the films indicate that the dielectric constant of the deposited film decreased with increasing C 4 F 8 flow rate which is in accord with the increase in the frequency of Si–O stretching mode. When the flow rate ratio of C 4 F 8 to TEOS is equal to 1.8, the dielectric constant of the film amounts to 2.35 at 1 MHz.