Microanalysis of a thin native oxide layer on silicon surfaces by parallel EELS

Abstract

It is known that a thin layer of so-called “native oxide” is formed immediately on clean silicon surfaces upon exposure to air at room temperature. The composition of native oxide, SiOx, is uncertain. Various experimental methods have yielded values less than 2 for x. Parallel energy loss spectrometers fitted to analytical electron microscopes with field emission sources provide sufficient spatial resolution (≤4nm) for direct quantitative analysis of native oxide films. In this note we report the first EELS analysis of native oxide on silicon.CZ Si {001} wafers, HF etched at room temperature and rinsed in doubly deionized water, were exposed to air until placed in an UHV chamber. A thin layer of Au wasthen deposited on Si surfaces, so that the native oxide layer was preserved between Si substrate and deposited Au film. Cross section TEM specimens were made in the usual way.