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 TiSi
₂
/n-Si (100) and NiPtSi
₂
/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 TiSi
₂
/n-Si (100) and NiPtSi
₂
/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.