Diagnostics of the silicon-insulator interface structure by optical second-harmonic generation

The second harmonic (SH) generation method has been applied to the study of the silicon-insulator (S-I) interface by in situ control of the etching process of SiO2 thermal oxide and Si3N4 silicon nitride insulator layers. It is shown, that the thin oxide interlayer, adjacent to the Si(111) epitaxial surface (with ∼ 1 nm thickness) exerts high influence on the reflected SH intensity. Various contributions to the nonlinear polarization in the S-I interface such as the static electric field, the inhomogeneous deformation and the crystalline oxide interlayer are considered.