Effects of density and bonding structure on dielectric constant of plasma deposited a-C:H films

Abstract

Bonding type and structure influence the variation of dielectric constant of a-C:H films dramatically. The incorporation of hydrocarbon with low polarization could form porous structures to further reduce polarization and density. The relations between the dielectric constant and the variation of structure, bonding type, and density of a-C:H are discussed. a-C:H films were deposited by para-xylene in an argon plasma with the deposition power of 100–300 W. The result shows that the density and dielectric constant of a-C:H films are in proportion to the deposition power. From FT-IR and Raman spectra, we found that Δ ε e was related to the H/C ratio and Δ ε o was affected by the amount of hydrocarbon radicals in the films. In addition, the dielectric constant also changed with film density due to the variation of dielectric volume, but the role of hydrocarbon radicals became more significant as the deposition power was increased.