Investigation of Plasma Polymerization Process to Produce Silicate Film with Structured Porosity

In this study, a fluorinated silicate film was produced by plasma polymerization using a radio frequency plasma system. In order to reduce the refractive index of the films, structured porosity was created in the film. The amount of impurities, optical absorption coefficient, surface roughness, the leakage current density and the threshold of the breakdown field were investigated. To investigate the effect of plasma polymerization process, fluoride gas type and working pressure, as well as placing the base for substrates were tested. The chemical bonding states of the films and the morphology of the films surface were investigated using the infrared Fourier transform spectrometer and atomic force microscope, respectively. In addition, the study of refractive index and absorption coefficient were also performed by spectroscopic ellipsometry. The results showed that the high purity fluorinated silicate film having structured porosity has ultra-low refractive index and the extinction coefficient lower than 10-4 , and increasing the pressure as well as placing the stand for silicon substrates causes to increase organic impurities, especially carbon bonds, thereby eliminating the structured porosity, which in total led to increase the refractive index (1.37 and 1.39) and the extinction coefficient (0.004 and 0.0005) of the films.