Vibrational spectroscopy characterization of low-dielectric constant SiOC:H films prepared by PECVD technique

Low-dielectric constant SiOC:H films were prepared by plasma enhanced chemical vapour deposition (PECVD) from trimethyl-silane (H-Si-(CH3)(3)) and ozone (O-3) gas mixture. The samples were preliminarily annealed at 400 degreesC in N-2 atmosphere and then in N-2 + He plasma. Afterwards, they were treated in vacuum at some fixed temperatures in the range between 400 and 900 degreesC. Structural investigations of the annealed films were carried out by means of vibrational spectroscopy techniques. FT-IR spectrum of a preliminarily treated sample shows absorption bands due to stretching modes of structural groups like Si-CH3 at similar to1270 cm(-1), Si-O-Si at 1034cm(-1) and C-H, in the region between 2800 and 3000 cm(-1). No significant spectral change was observed in the absorption spectra of samples annealed Lip to 600 degreesC, indicating that the preliminarily treated film retains a substantial structural stability up to this temperature. Above 600 degreesC, absorption spectra show a strong quenching of H-related peaks while the band due to Si-O-Si anti-symmetric stretching mode shifts towards higher energy, approaching the value observed for thermally grown SiO2. Raman spectra of samples treated at temperatures T greater than or equal to 500 degreesC exhibit both D and G bands typical of sp(2)-hybridised carbon, due to the formation of C-C bonds within the film which is accompanying the release of hydrogen. The intensity of D and G bands becomes more pronounced in samples annealed at higher temperatures, thus suggesting a progressive precipitation of carbon within the oxide matrix. (C) 2004 Elsevier Ltd. All rights reserved.