Analytical Model of Contact Resistance in Vertically Stacked Nanosheet FETs for Sub-3-nm Technology Node

For the first time, a novel analytical model of contact resistance (Rcontact) in vertically stacked nanosheet FETs (NSHFETs) with a silicide/Si (100) contact for a sub-3-nm node is presented. Generally, (Rcontact) consists of the interface resistance (Rinterface) and spreading resistance ({Rspread). Herein, a new model of Rinterface of silicide/Si (100) contact, which simultaneously considers the source/drain (S/D) doping concentration (Nsi), Schottky barrier height (SBH), and SBH lowering, is demonstrated simultaneously. In addition, a new model of ({Rspread) that divides S/D into multiple resistance components for vertically stacked NSHFETs is suggested. In vertically stacked NSHFET with 3-nm node, for TiSi2/n-Si (100) and NiPtSi2/p-Si (100) contacts, ({Rspread) shows more than 50.0% higher values compared to Rinterface. On the other hand, 3-nm node FinFET with TiSi2/n-Si (100) and NiPtSi2/p-Si (100) contacts, ({Rspread) shows more than 53.7% lower values compared to (Rcontact). The results show that ({Rspread) becomes dominant in (Rcontact) compared to Rinterface when using NSHFETs, in contrast to the conventional FinFETs in which Rinterface is dominant in (Rcontact). The high ({Rspread) of the NSHFET is mainly caused by the low nanosheet thickness and vertical pitch between the nanosheets. This study provides critical insights into the design of the source/drain of NSHFET for sub-3-nm CMOS technology.