Analytic Model of S/D Series Resistance in Trigate FinFETs With Polygonal Epitaxy

In this paper, a simple but accurate model is presented to analyze source/drain (S/D) series resistance in trigate fin field-effect transistors, particularly on triangular or pentagonal rather than rectangular epitaxy. The model includes the contribution of spreading, sheet, and contact resistances. Although the spreading and sheet resistances are evaluated modifying standard models, the contact resistance is newly modeled using equivalent models of lossy transmission lines and transformations of 3-D to 2-D geometry. Compared with series resistance extracted from 3-D numerical simulations, the model shows excellent agreement, even when the S/D geometry, silicide contact resistivity, and S/D doping concentration are varied. We find that the series resistance is influenced more by contact surface area than by carrier path from the S/D extension to the silicide contact. To meet the series resistance targeted in the semiconductor roadmap, both materials and geometry will need to be optimized, i.e., lowering the silicide contact resistivity and keeping high doping concentration as well as maximizing the contact surface area, respectively.