An investigation of the stoichiometry and impurity content of thin silicon oxide films using Rutherford scattering of MeV α-particles

Abstract

It is described how the Rutherford scattering of MeV α‐particles may be used to study the stoichiometry and impurity content of thin silicon oxide films. The relative concentrations of silicon to oxygen can be measured to ≈ 5%, and in the most favourable cases, impurity concentrations as low as ≈1018 ions cm−3 can be measured.

Thin-film analysis using Rutherford scattering

“…The electrical properties of these thin films exhibit widely differing behaviour for apparently identical starting materials and fabrication procedures. In a previous publication (Morgan and Gittins 1972) we showed that Rutherford scattering can be used to characterize thin SiO, films. The energy spectrum for a-particles scattered from an Si/SiOz/Au specimen.…”

“…The removal of the background spectrum has enabled some 12 impurity peaks to become visible without any masking from the background. In the fabrication of this oxide there was no apparent difference from the procedures which have been used consistently to fabricate SiOz (Morgan and Gittins 1972). The origin of the A1 peak is boat contamination.…”

“…Unfortunately, however, in the majority of this early work, structural information was not available. In an earlier publication (Morgan and Gittins 1972) we outlined the results of a preliminary study of the feasibility of using the Rutherford scattering technique as a quantitative tool for the analysis of thin siliconoxide films. We now describe the extension of this work to a number of binary compound systems which are of current interest because of their novel switching and memory effects (Dearnaley et aZ1971).…”

“…The basic principles of the Rutherford scattering technique have been described in detail in a previous publication (Morgan and Gittins 1972), and are the subject of a recent review paper (Chu et a Z 1973). From the spectra we obtain the following information:…”