Study of fluorinated amorphous carbon films prepared by electron cyclotron resonance chemical vapor deposition

Abstract

Fluorinated amorphous carbon(a-C:F) films were deposited using C4F8 and CH4 as precursor gases by electron cyclotron resonance chemical vapor deposition (ECR-CVD). Analysis of chemical compositions and bond structures by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) shows that the loss of CF3 and C—C termination bonds are liable for inducing reduction of film thickness after heat treatment through out-gassing process. The dielectric constant of a-C:F films increases due to increased electronic polarization and enhanced film density and the interface trap density decreases from (5—9)×1011eV-1cm-2 to (4—6)×1011eV-1cm-2 after 300℃ annealing in a nitrogen environment. The current-voltage characteristics of α-C:F films was explained by ohmic conduction at low fields and Poole-Frankel conduction at high electric fields. The trap energy of the traps at band tails formed by the delocalized π electrons decreases after annealing, leading to the increase of leakage current due to field-enhanced thermal excitation of trapped electrons into the conduction band.