FT-IR-RAS ANALYSIS OF THE STRUCTURE OF THE SiO2/Si INTERFACE

Abstract

A thin thermally grown silicon dioxide film was analyzed by Fourier-Transform Infrared Reflection Absorption Spectroscopy (FT-IR-RAS). In order to separate the features of the bulk structure of SiO2 film and of the oxide structure in the vicinity of the SiO2/Si interface, the IR-RAS spectra of a thick oxide film of 49nm in thickness, which contained little interface structure, and that of a thin oxide film of 2.5nm thickness which contained more interface structure were compared with each other. To avoid the effects of differences in optical paths due to oxide thickness, the dielectric function of the thick oxide was calculated and used to simulate the spectrum of a thin oxide film which had the dielectric function of the thick oxide and a TO phonon peak area nearly equal to that of the 2.5nm thin oxide film. The reflectance of the LO phonon peak at about 1255cm−1 of the calculated spectra was larger than that of the measured spectra but the reflectance from 1200cm−1 to 1100cm−1 of the measured spectra was larger than that of the calculated spectra. Therefore the feature at about 1255cm−1 on the IR-RAS chart reflects bulk SiO2 structure and that from 1200 to 1100cm−1 reflects the structure of the SiO2/Si interface.