VTH shift mechanism in dysprosium (Dy) incorporated HfO2 gate nMOS devices

We discuss temperature-dependent 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 V_FB 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 V_FB/V_TH 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. Charge trapping characteristics in relation to the stress-induced flatband shift and SILC are discussed with a band diagram. The higher effective barrier height of Dy₂O₃, which is around 2.32 eV, calculated from the F-N plot, accounts for the reduced leakage current in Dy incorporated HfO₂ nMOS devices. The lower trap generation rate by the reduced hole trap density and the reduced hole tunneling of the Dy-doped HfO₂ dielectric demonstrate the high dielectric breakdown strength by weakening the charge trapping and defect generation during the stress.