Effects of acetylene on property of plasma amorphous carbon films

Amorphous carbon film (a-C:H) deposited by plasma-enhanced chemical vapor deposition is a potential candidate of low-k material for the requirements of ULSI device. The bonding structure and element of a-C:H films influence dielectric property dramatically. Para-xylene was utilized as carbon precursor added with acetylene to deposit a-C:H films at ambient temperature. The bonding type, network structure and optical gap of films were analyzed by FT-IR, Raman and UV–Visible spectroscopy, respectively. The purpose is to determine the influences of acetylene concentration on the structures and bonding types of amorphous carbon film. The results show that the increases of acetylene concentration and deposition power increase the deposition rate but decrease the optical gap and density. Thus, the films deposited with sp2 and sp3 hydrocarbon bonds have lower polarized bonds and porous structure of low density, which are both responsible for the variation of dielectric constant.