Bonding configuration and density of defects of SiOxHy thin films deposited by the electron cyclotron resonance plasma method

• Published in: Journal of applied physics 2003-12, Vol.94 (12), p.7462-7469
• Main Authors: San Andrés, E., del Prado, A., Mártil, I., González-Dı́az, G., Bravo, D., López, F. J., Fernández, M., Bohne, W., Röhrich, J., Selle, B., Sieber, I.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1626798

The composition, bonding configuration, hydrogen content, and paramagnetic defects of SiOxHy thin films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH4 and O2 as precursor gases. The film composition was measured by heavy ion elastic recoil detection analysis and energy dispersive x-ray spectroscopy. Suboxide films with compositions ranging from SiO2 to SiH0.38 were obtained. Infrared spectroscopy showed the presence of different Si–O and Si–H vibration modes. The usual estimation of the oxygen to silicon ratio by the wave number of the Si–O–Si stretching band was not accurate for films far from stoichiometry. These off-stoichiometric films also showed a broader Si–O–Si stretching peak than the stoichiometric ones, indicating a higher bonding disorder. The position of the Si–O–Si bending and rocking modes did not depend on the film composition. On the other hand, the peak position of the Si–H modes were found strongly dependent on the Si environment. By single-wavelength ellipsometry at λ=632.8 nm the refractive index n was found to range between 1.45 (SiO2) and 2.04 (SiO0.06H0.36). Electron spin resonance measurements showed that stoichiometric films presented the well known E′ center (⋅Si≡O3) with concentrations in the 1016–1017 cm−3 range, while for Si-rich films (x≪1) the Si dangling bond center (SiDB, ⋅Si≡Si3) was the only detectable defect, with concentrations in the 1018–1019 cm−3 range. In near-stoichiometric films both E′ and SiDB centers were found.