Hafnium silicide formation on Si(100) upon annealing

Abstract

High dielectric constant materials, such as $\mathrm{Hf}{\mathrm{O}}_{2}$, have been extensively studied as alternatives to $\mathrm{Si}{\mathrm{O}}_{2}$ in new generations of Si based devices. Hf silicate∕silicide formation has been reported in almost all literature studies of Hf based oxides on Si, using different methods of preparation. A silicate interface resembles close to the traditional $\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_{2}$. The silicate very likely forms a very sharp interface between the Si substrate and the metal oxide, and would be suitable for device applications. However, the thermal instability of the interfacial silicate∕oxide film leads to silicidation, causing a dramatic loss of the gate oxide integrity. Despite the importance of the Hf silicide surface and interface with Si, only a few studies of this surface are present in the literature, and a structural determination of the surface has not been reported. This paper reports a study of the Hf silicide formation upon annealing by using a combination of XPS, LEED, and x-ray photoelectron diffraction (XPD) analyses. Our results clearly indicate the formation of a unique ordered Hf silicide phase $(\mathrm{Hf}{\mathrm{Si}}_{2})$, which starts to crystallize when the annealing temperature is higher than $550\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$.