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 ( ${R}_{\text{contact}}$ ) in vertically stacked nanosheet FETs (NSHFETs) with a silicide/Si (100) contact for a sub-3-nm node is presented. Generally, ${R}_{\text{contact}}$ consists of the interface resistance ( ${R}_{\text{interface}}$ ) and spreading resistance ( ${R}_{\text{spread}}$ ). Herein, a new model of ${R}_{\text{interface}}$ of silicide/Si (100) contact, which simultaneously considers the source/drain (S/D) doping concentration ( ${N}_{\text{si}}$ ), Schottky barrier height (SBH), and SBH lowering, is demonstrated simultaneously. In addition, a new model of ${R}_{\text{spread}}$ 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, ${R}_{\text{spread}}$ shows more than ~50.0% higher values compared to ${R}_{\text{interface}}$ . On the other hand, 3-nm node FinFET with TiSi₂/n-Si (100) and NiPtSi₂/p-Si (100) contacts, ${R}_{\text{spread}}$ shows more than ~53.7% lower values compared to ${R}_{\text{contact}}$ . The results show that ${R}_{\text{spread}}$ becomes dominant in ${R}_{\text{contact}}$ compared to ${R}_{\text{interface}}$ when using NSHFETs, in contrast to the conventional FinFETs in which ${R}_{\text{interface}}$ is dominant in ${R}_{\text{contact}}$ . The high ${R}_{\text{spread}}$ 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.