Mechanism of $VFB/VTH$ shift in Dysprosium incorporated $HfO2$ gate dielectric n-Type Metal-Oxide-Semiconductor devices

The authors discuss temperature-dependent dysprosium (Dy) diffusion and the diffusion-driven Dy-silicate formation process in Dy incorporated $HfO2$⁠. The Dy-induced dipoles are closely related to the Dy-silicate formation at the high-$k/SiO2$ interfaces since the $VFB$ shift in $Dy2O3$ is caused by the dipole and coincides with the Dy-silicate formation. Dipole formation is a thermally activated process, and more dipoles are formed at a higher temperature with a given Dy content. The Dy-silicate related bonding structure at the interface is associated with the strength of the Dy dipole moment and becomes dominant in controlling the $VFB/VTH$ shift during the high temperature annealing in the $Dy–Hf–O/SiO2$ gate oxide system. Dy-induced dipole reduces the degradation of the electron mobility.