XPS and SIMS analysis of gold suicide grown on a bromine passivated Si(111) substrate

Abstract

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 363°C, epitaxial layer-plus-island mode growth of gold suicide 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 μm and the silicide/Si interface is abrupt. XPS measurements were made after sputtering the sample surface at constant intervals of time. Si 2p, Au 4f, C 1s and O 1s photoelectrons were detected. XPS spectra of Si 2p are resolved into three peaks corresponding to bulk Si, Si in suicide and Si in oxide. The Au 4f7/2 peak in the suicide is shifted by 1-1.2 eV towards higher binding energy compared to metallic Au. The shift of Si 2p towards the higher binding energy in the suicide is understood from the higher electronegativity of Au, while the shift of Au 4/7/2 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 suicide is sandwiched between a thin (≃ 2.8 nm) SiO2 layer and the Si(111) substrate. © 1999 Elsevier Science B.V. All rights reserved.