Infrared spectroscopic analysis of reactively formed La-silicate interface layer at La2O3/Si substrates

Infrared spectroscopic analyses of reactively formed La-silicate gate dielectrics between La2O3 and Si substrates are conducted with the attenuated total reflection configuration. The formation of a La-silicate interface layer at the surface of Si(100) has been confirmed with an annealing temperature of 300 °C and the layer has grown with increasing the annealing temperature. The strain in the SiO4 tetrahedral network in the La-silicate interface layer, measured from longitudinal optical phonon vibration, showed relaxation when annealed at over 600 °C, suggesting a decrease in glass transition temperature owing to the presence of La atoms in the network. A strong correlation between the relaxation and the interface state density has been confirmed. The same relaxation trend with annealing temperature has been confirmed for Si(110) and (111) surfaces as well.