Spectroscopic ellipsometry study of parylene AF4

The spectroscopic ellipsometry study of parylene AF4 films was performed in a broad optical range from mid-infrared (MIR) to deep ultra-violet (DUV) light. The wavelength-dependent refractive index and extinction coefficients were determined using the spectral fitting of the modeled and experimental data. The established optical model, based on the classical oscillator theory, comprised of four Gaussian and one Tauc-Lorentz peak functions for the UV and Brendel-Bormann oscillations – in MIR regions enables fast and precise thickness determination of parylene coatings as well as the electronic properties of the molecules by monitoring the alteration of the dielectric function. The thermal treatment of the films in ambient atmosphere up to 450°C showed the overall stability of the parylene film with only negligible alteration of the optical transition energies and thus its refractive index.