Statistical Simulation Study of Metal Grain-Orientation-Induced MS and MIS Contact Resistivity Variability for 7-nm FinFETs

This paper presents a statistical simulation study of contact resistivity ( $\rho _{c}$ ) variability (CRV) of TiN and TaN metal–semiconductor (MS) and metal–interfacial layer–semiconductor (MIS) n-Ge(Si) source/drain (S/D) contacts resulting from variation in contact metal work function ( $\phi _{m}$ ) due to its different grain orientations, and its impact on FinFET performance at 7-nm node using 3-D TCAD simulations. Fermi-level unpinning enables MIS contacts to exhibit lower $\rho _{c}$ than MS contacts but increases their sensitivity to $\phi _{m}$ variation leading to higher CRV. CRV is shown to get worse with device scaling, especially for MIS contacts. However, increasing S/D doping, reducing grain size, and doping the interfacial layer (for MIS contacts) demonstrate reduction in CRV. At high S/D dopings, TiN MS contacts on Ge as well as Si meet International Technology Roadmap for Semiconductors requirements with nearly the same $\rho _{c}$ as MIS contacts but with significantly lower CRV.