XPS and SIMS analysis of gold silicide grown on a bromine passivated Si 111/substrate

When a thin film of Au ;100 nm.deposited under high vacuum conditions on a chemically prepared Br-passivated Si 111.substrate was annealed around 3638C, epitaxial layer-plus-island mode growth of gold silicide was observed along with some unreacted gold in stringy patterns. This unreacted gold was removed by etching the sample in aqua regia. X-ray photoelectron spectroscopy XPS.and secondary ion mass spectrometry SIMS.measurements were carried out on these samples. SIMS results reveal that the height of the islands is about 1.2 mm and the siliciderSi interface is abrupt. XPS measurements were made after sputtering the sample surface at constant intervals of time. Si 2 p, Au 4f, C 1s and O 1s photoelectrons were detected. XPS spectra of Si 2 p are resolved into three peaks corresponding to bulk Si, Si in silicide and Si in oxide. The Au 4 f7r2 peak in the silicide is shifted by 1–1.2 eV towards higher binding energy compared to metallic Au. The shift of Si 2 p towards the higher binding energy in the silicide is understood from the higher electronegativity of Au, while the shift of Au 4 f7r2 peak towards higher binding energy is known to be due to d-electron depletion to form an sd hybrid. The XPS peak intensity profile with sputtering time indicates that the thin uniform layer ;5.5 nm.of gold silicide is sandwiched between a thin ;2.8 nm.SiO2 layer and the Si 111. substrate. q1999 Elsevier Science B.V. All rights reserved.