Low dielectric fluorinated amorphous carbon thin films grown from C 6F 6 and Ar plasma

Abstract

Fluorinated amorphous carbon (a-C:F) thin films were synthesized for applications in low dielectric constant intermetal dielectric materials. The deposition was carried out in a capacitively coupled, asymmetric plasma reactor using hexafluorobenzene (C 6F 6) as the source gas and argon as the carrier gas. The effects of applied rf power on the electric, optical and mechanical properties of the a-C:F films were investigated. The bonding structures and properties of the films were evaluated by FTIR spectrometry, UV-Vis spectrophotometry and stress measurements. The films exhibit a dielectric constant as low as 2.0 and have high transparency in the visible range. The deposition rate of the a-C:F films increases, reaches a maximum, and then gradually decreases with increasing rf power. High rf power raises the negative self-bias voltage at the substrate and leads to an increase in the content of conjugated CC bonds in the a-C:F films. As the negative self-bias voltage at the substrate is increased, the dielectric constant, residual stress, and graphitization of the a-C:F films are increased while the optical energy gap is decreased.