A photoluminescence of low-K SiOCH films, prepared by PECVD

Carbon-doped hydrogenated silicon oxide (SiOCH) low-k films have been prepared using 13.56 MHz discharge in trimethylsilane (3MS) - oxygen gas mixtures at 3, 4, and 5 Torr sustained with RF power densities 1.3 - 2.6 W/cm². The atomic structure of the SiOCH films appears to be a mixture of the amorphous SiO₂-like and the partially polycrystalline SiC-like phases. Results of the infrared spectroscopy and atomic force microscopy reflect the increment in the volume fraction of the SiC-like phase from 0.22 - 0.28 to 0.36 - 0.39 as the RF power increment. Steady-state near-UV laser-excited (364 nm wavelength, 40±2 mW) photoluminescence (PL) has been studied at room temperatures in the visible ( 1.8 eV - 3.1 eV) range of photon energies. Two main bands of the PL signal (at the photon energies of 2.5 - 2.6 eV and 2.8 2.9 eV) are observed. Intensities of the both bands are changed non-monotonically with RF power, whereas the bandwidth of ∼0.1 eV remains almost invariable. It is likely that the above lines are originated by the radiative recombination involving D₁ centres in the crystalline SiC-like phases. Explanation of the PL intensity dependence on the RF power density can be based on results of studies of morphology of the SiOCH films.