Electrical and optical properties of amorphous fluorocarbon films prepared by plasma polymerization of perfluoro-1,3-dimethylcyclohexane

Abstract

The electrical and optical properties of amorphous fluorocarbon films (a-C:F) prepared by plasma polymerization have been investigated. Perfluoro-1,3-dimethylcyclohexane was introduced into a parallel plate plasma reactor operating at 13.56 MHz to deposit a-C:F films. Transparent a-C:F films with an F/C ratio of 2 were prepared at lower power densities of 10–300 mW/cm2 at deposition rates of 4–10 nm/min. The films have a low surface energy of 15 mN/m and are thermally stable up to 210 °C. The coatings exhibit low refractive index of 1.38, low dielectric constant of 2.3, and high transmittance in the visible range. The electret properties were evaluated by measuring the decay of a positive surface potential (SPD) on 25 μm thick a-C:F films. High rf power densities lead to an increased formation of conjugated C–C double bonds affecting the transmittance and SPD characteristic. However, the relative low thermal stability, insufficient planarization, and charge storage capabilities limit the applications of the a-C:F films for microelectronic and electrical applications.