Study on the characteristics of ThioPP thin films for low-κ applications

The thiophene plasma polymer was deposited on silicon(100) substrates by PECVD (Plasma Enhanced Chemical Vapor Deposition) with homemade stainless steel vacuum chamber. Thiophene was utilized as organic precursor with hydrogen gas as bubbling gas. Argon gas was used as a carrier gas. To analyze the electrical properties of the plasma polymerized thin films, the plasma-polymer thin films were grown under various RF power condition. The as-grown plasma-polymer thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), measuring the capacitance, impedance analyzer, ellipsometry, Fourier Transform Infrared spectroscopy (FT-IR), and water contact angle measurement. AFM and SEM images showed smooth surfaces of thin films with increasing RF power. An impedance analyzer was utilized for the measurements of I-V curves (for leakage current density) and capacitance (for dielectric constant). Refractive indices were increased by increasing RF power. The IR spectra showed that the plasma polymer thin films have totally different chemical functionalities from liquid thiophene precursor, as well as the changing chemical functionalities of the thin films caused by various RF powers. The best dielectric constant is 2.52 in this study.