Platinum silicide phase transformations controlled by a nanometric interfacial oxide layer

Abstract

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 °C). Silicide films grown through an interfacial oxide layer consist of two adjacent Pt 2Si 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 °C. The Pt 2Si layer, to the contrary, remains unchanged up to 700 °C at least. The existence and stability of this layer at higher temperatures, together with the epitaxial relationship at the Pt 2Si/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 °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.