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

For the first time, after considering the thermodynamic properties (evaluated by the molar Gibbs energy of oxide formation, Delta_OxideG) and the electronegativity (chi) 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 Delta_OxideG of dopant (Delta_Ox-dopG) is more negative than that of host gate oxide (Delta_Ox-hostG). Or else, chi 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.