Characterization of polymer-like thin films deposited on silicon and glass substrates using PECVD method

Polymer-like thin films have been deposited on glass and silicon substrates at temperatures in the range 300-673 K, by a plasma enhanced chemical vapor deposition (PECVD) method using thiophene (C₄H ₄S) as a precursor. A power with radio frequency (13.56 MHz) was applied for the ignition of the plasma, and hydrogen and Ar(argon) were used as the bubbler and the carrier gases, respectively. In order to compare physical properties of the as-grown thin films, an effect of the plasma power and deposition temperature on the dielectric constant and thermal stability were mainly studied. XRD and FT-IR studies revealed that the as-grown films at 373 K have highly oriented amorphous polymer structure. XPS revealed that the polymerized thin films have the same stoichiometric ratio (8:1) between C and S, indicating that dimer-like thin films were mainly grown under our experimental condition. From the electrical properties measurements such as I-V and C-V characteristics, we knew that the relative dielectric constants increased from 2.96 to 4.0 when the RF power was increased up to 200 W. Moreover, the leakage current density was increased with increasing RF power and deposition temperature. The maximum deposition rate obtained was 110 nm/min for the polymerized thin film deposited at 300 K and 100 W. The activation energy for polymer-like thin film deposition calculated from the Arrhenius plot was -6.9 kJ/mol, signifying that a diffusion control process was the rate-determining mechanism.