Impact of Lanthanum-Induced Dipoles on the Tunneling and Dielectric Properties of Gate-Stack

Threshold voltage ( ${V_{t}}$ ) engineering is critical and challenging in the advanced logic devices. Inducing interface dipoles by the incorporation of dopants into the gate dielectrics is an emerging scheme to modulate the threshold voltage. However, the impact of those dipoles on gate-stack performance is of great concern. In this work, we present the first-principles calculations of dielectric constant and tunneling current of high- ${k}$ gate-stack with lanthanum (La) dopants. It is found that incorporation of La improves the local dielectric constant as well as the equivalent oxide thickness (EOT), but degrades the gate leakage current. The calculated results are consistent with the reported experimental data. Furthermore, by analyzing the transmission coefficients and band alignment across the gate-stack, a theoretical explanation for the change of gate leakage current is provided.