Investigation of fluorocarbon thin films as dielectric materials for electronic applications

We investigated fluorocarbon thin films as dielectric materials for electronics. Films were deposited by RF magnetron sputtering of PTFE. Their structural properties were investigated using XPS, FTIR, and TGA analysis. Films have a stoichiometry close to CF₂. They incorporate C-C, CF, CF₂ and CF₃ bonds (11%, 61%, 20%, and 8% respectively). Films start to decompose around 200°C. Insulating properties were assessed by studying absorption currents and their temperature dependence. The resistivity is around 10¹⁶ Ω.cm and it increases with an activation energy of 0.45 eV. The complex dielectric constant was measured from 0.1 Hz to 1 MHz, as a function of temperature. The dielectric constant is around 2.3 at radio frequencies and 1.8 at optical frequencies. The background loss factor is about 0.7% in the RF range. The dielectric constant decreases with the reverse of the temperature, as predicted by a Debye law. Surface potential decay was monitored after corona charging. Decay times around 10 hours are measured.