Study of defects in silicon dioxide films on Si(100) by a variable-energy positron beam

Amorphous SiO₂ films grown by both thermal oxidation and plasma chemical vapor deposition (CVD) in a tetraethylorthosilicate and O₂ atmosphere were studied using variable-energy positron annihilation spectroscopy and infrared (IR) spectroscopy. For thermally grown SiO₂ layers with growth temperatures of over 1000 °C it was found that the measured Doppler broadening parameter was identical for both wet and dry growth atmospheres. The measured Doppler broadening parameter in the case of SiO₂ prepared by plasma CVD was found to be strongly influenced by the substrate temperature during deposition. For a substrate growth temperature of 600 °C, the data are essentially identical to those of the thermally grown oxide layers. IR analysis revealed that the concentration of Si-OH in the SiO₂ layer is affected by the substrate temperature during growth. The level of the Doppler broadening parameter in the SiO₂ film exhibited changes that can be correlated with this Si-OH concentration. We thus show that the concentration of Si-OH in amorphous SiO₂ film is a factor that may affect the Doppler broadening parameter.