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 (Pc) 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 (φ
_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 P
_c
than MS contacts but increases their sensitivity to φ
_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 Pc as MIS contacts but with significantly lower CRV.