The effect on the thermal and dielectric properties of incorporating benzene rings in hydrogenated amorphous carbon(a-C:H) films was investigated. The benzene rings were introduced intoa-C:H films by using plasma-enhanced chemical vapor deposition and aromatic source compounds. Thea-C:H film that contained benzene rings had thermal stability up to 400 °C and a low-dielectric constant of 3.0. The difference in the dielectric constant and thermal stability ofa-C:H films appeared to be due to the hydrogen concentration of the films. ©1997 American Institute of Physics.