Structural and dielectric properties of parylene-VT4 thin films

Abstract

58% semi-crystalline thin parylene-VT4 (eH2CeC6F4eCH2 )n films, have been investigated by dielectric spectroscopy for temperature and frequency ranges of [ 120 to 380 C] and [0.1e105 Hz] respectively. The study comprises a detailed investigation of the dielectric constant, dielectric loss and AC conductivity of this fluoropolymer. Dielectric behavior of parylene-VT4 is represented by a low dielectric constant with values in the range of 2.05e2.35 while the dielectric losses indicate the presence of two relaxation processes. Maxwell Wagner Sillars (MWS) polarization at the amorphous/crystalline interfaces with activation energy of 1.6 eV is due to the oligomer orientation. Electrical conductivity obeys to the well-known Jonscher law. The plateau in the low frequency part of this conductivity is temperature-dependent and follows an Arrhenius behavior with activation energy of 1.17 eV (deep traps) due to the fluorine diffusion. Due to its thermal stability with a high decomposition temperature (around 400 C under air and 510 C under nitrogen) and due to its good resistivity at low frequency (1015e1017 U m 1), parylene-VT4 constitutes a very attractive polymer for microelectronic applications as low k dielectric. Moreover, when parylene-VT4 is subjected to an annealing, the dielectric properties can be still more improved.