Understanding and prediction of EWF modulation induced by various dopants in the gate stack for a gate-first integration scheme

Abstract

For the first time, after considering the thermodynamic properties (evaluated by the molar Gibbs energy of oxide formation, Δ OxideG) and the electronegativity (χ) for both the dopants (via ion implantation, thin capping layer or co-deposition) and host materials in the gate stack, a practical model to understand the effective work function (EWF) modulation induced by various dopants is proposed. It is found that the dopant oxide will determine the EWF if the ΔOxideG of dopant (ΔOx-dopG) is more negative than that of host gate oxide (ΔOx-hostG). Or else, χ difference between dopants and host materials will play a more critical role for determining the EWF. This model can serve as a guideline for understanding the EWF modulation by various dopants and to select appropriate gate stack materials for the gate-first technology. © 2008 IEEE.