Chemical Structure, Optical and Dielectric Properties of PECVD SiCN Films Obtained from Novel Precursor

Abstract

A phenyl derivative of hexamethyldisilazane—bis(trimethylsilyl)phenylamine—was first examined as a single-source precursor for SiCN film preparation by plasma enhanced chemical vapor deposition. The use of mild plasma (20 W) conditions allowed the preparation of highly hydrogenated polymeric-like films. The synthesis was carried out under an inert He atmosphere or under that of NH3 with the deposition temperature range from 100 to 400 °C. The chemical bonding structure and elemental composition were characterized by Fourier-transform infrared spectroscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. The surface morphology was investigated by scanning electron microscopy. Ellipsometric porosimetry, a unique high-precision technique to investigate the porosity of thin films, was applied to examine the porosity of SiCN samples. The films were found to possess a morphologically homogenous dense defect-free structure with a porosity of 2–3 vol.%. SiCN films were studied in terms of their optical and dielectric properties. Depending on the deposition conditions the refractive index ranged from 1.53 to 1.78. The optical bandgap obtained using UV-Vis spectroscopy data varied from 2.7 eV for highly hydrogenated polymeric-like film to 4.7 eV for cross-linked nitrogen-rich film. The dielectric constant was found to decrease from 3.51 to 2.99 with the rise of hydrocarbon groups’ content. The results obtained in this study were compared to the literature data to understand the influence of precursor design to the optical and electrical properties of the films.