Characterization of low-dielectric-constant SiOC thin films deposited by PECVD for interlayer dielectrics of multilevel interconnection

Abstract

Low-dielectric-constant (k) SiOC films were deposited on p-type (100) Si substrates by radio frequency (RF) PECVD with a bis-trimethylsilylmethane (BTMSM) precursor and oxygen gas. As more carbon was incorporated into the SiOC film, both the film density and refractive index decreased. This is because the decrease in film density on adding carbon in SiOC films resulted from termination of the SiO bonding network by replacing oxygen atoms with hydrocarbon groups. The bonding characteristics of low-k SiOC and SiOF films were investigated by Fourier-transform infrared (FTIR) spectroscopy. The SiO stretching vibration mode in SiOF films shifted to higher wavenumber with increasing fluorine incorporation, while that in SiOC films shifted to lower wavenumber as the carbon content increased. The origin of the low k of SiOC films was also investigated by determining the electronic, ionic and dipolar contributions. It was found that the low k of SiOC films mainly results from a reduction of the ionic contribution due to a decrease in SiO bonds in the films. Investigating the compatibility with integration processes showed that modification of the conventional process was required to improve the etch characteristics of the SiOC film. Post-deposition treatment of SiOC films in hydrogen plasma was effective. The results of this study show that SiOC film is very promising low-k material for interlayer dielectrics of multilevel interconnection.