Platinum silicide phase transformations controlled by a nanometric interfacial oxide layer

Nanometer-thick platinum silicide films were obtained by solid-state thermal reaction films in the presence of an interfacial native silicon oxide layer. They were studied using High-Resolution Transmission Electron Microscopy (HRTEM) and selected-area electron diffraction. Ten nm-thick sputtered Pt films reacted with the Si substrate through the oxide pinholes, which influenced the Pt-Si reaction over the whole annealing temperature range examined (165-800 degrees C). Silicide films grown through an interfacial oxide layer consist of two adjacent Pt2Si and PtSi layers in contrast with films obtained on oxide-free wafers, which show only PtSi grains. The continuous PtSi film transforms to an epitaxial, island-type film after annealing at 650 degrees C. The Pt2Si layer, to the contrary, remains unchanged up to 700 degrees C at least. The existence and stability of this layer at higher temperatures, together with the epitaxial relationship at the Pt2Si/PtSi interface help preserve the continuity and the good electrical conductance of silicide films obtained in presence of an interfacial oxide layer even above 700 degrees C. Epitaxial relationships between thin and very thin (3-5 nm) platinum silicide films and the Si substrates have also been studied directly from HRTEM images. Several orientation relationships for the PtSi/Si interface are discussed. (C) 2008 Elsevier B.V. All rights reserved.