Thermodynamic stability of high-K dielectric metal oxides ZrO2 and HfO2 in contact with Si and SiO2

Abstract

We present theoretical and experimental results regarding the thermodynamic stability of the high-k dielectrics ${\mathrm{ZrO}}_2$ and ${\mathrm{HfO}}_2$ in contact with Si and ${\mathrm{SiO}}_2.$ The ${\mathrm{HfO}}_2/\mathrm{Si}$ interface is found to be stable with respect to formation of silicides whereas the ${\mathrm{ZrO}}_2/\mathrm{Si}$ interface is not. The ${\mathrm{metal–oxide/SiO}}_2$ interface is marginally unstable with respect to formation of silicates. Cross-sectional transmission electron micrographs expose formation of nodules, identified as silicides, across the polycrystalline ${\mathrm{silicon/ZrO}}_2/\mathrm{Si}$ interfaces but not for the interfaces with ${\mathrm{HfO}}_2.$ For both ${\mathrm{ZrO}}_2$ and ${\mathrm{HfO}}_2,$ the x-ray photoemission spectra illustrate formation of silicate-like compounds in the ${\mathrm{MO}}_2/{\mathrm{SiO}}_2$ interface.