Phase formation sequence and cobalt behavior in the Ni0.9 Co0.1 system during the thin film solid-state formation.

Abstract In this work, the solid-state reaction between a 7 nm thick Ni 0.9 Co 0.1 film and a silicon substrate has been studied. By combining various characterization methods (e.g. sheet resistance measurement, X-ray reflectivity, X-ray diffraction), a comprehensive phase sequence of the NiCo silicide formation has been proposed. At low temperature, we observed the formation of metal-rich Ni 2 Si-like phases: δ -(NiCo) 2 Si and θ -(NiCo) 2 Si. Contrary to Ni 0.9 Pt 0.1 based silicides, the δ -Ni 2 Si phase appears before the θ -Ni 2 Si one. Beyond 320 °C, the (NiCo)Si monosilicide formation is initiated and this latter is complete at 400 °C. The presence of Co strongly decreases the NiSi 2 formation temperature. This early formation of disilicide allows avoiding film agglomeration and enhances the thermal stability of NiSi silicide. Complementary studies using wavelength dispersive X-ray fluorescence allowed studying the cobalt behavior and highlighted the formation of a Co composition gradient into the metal-rich silicide phases at relatively low temperature (220–260 °C). Graphical abstract Unlabelled Image Highligh t s • Solid-state reaction between Ni 0.9 Co 0.1 alloy and Si has been fully studied. • The first Ni-rich phase to form is the δ-Ni 2 Si then it is followed by the θ-Ni 2 Si one. • The presence of Co strongly decreases the NiSi 2 formation temperature. • A Co composition gradient into the metal-rich silicide phases has been highlighted. [ABSTRACT FROM AUTHOR]