Local atomic structure at thermally grown Si/SiO 2 interfaces

Abstract

This paper presents an experimental study of the properties of SiO 2 and Si, in the immediate vicinity of thermally grown SiO 2/Si interfaces. We have examined properties of the SiO 2 films, including the center frequency and width of the SiO IR-active bond-stretching vibration, the optical index of refraction at 632.8 nm, and the intrinsic growth stress, as well as the photoreflectance and Raman scattering of the Si substrate at the growth interface. We have interpreted the temperature and thickness dependence of these properties in terms of a model which includes the molar volume mismatch between the SiO 2 and Si at the growth interface, and visco-elastic relaxation of the oxide. We conclude that the thermal history of SiO 2 films is generally non-homogeneous due to differences between the processing times, and the times for visco-elastic relaxation of the interface-generated stress. Even under conditions approaching a homogeneous thermal history, there are still significant stress gradients in the SiO 2 und underlying Si in the immediate vicinity of the SiO 2/Si interface.