Analytical Model of Contact Resistance in Vertically Stacked Nanosheet FETs for Sub-3-nm Technology Node
Seung-Geun Jung, Jeong‐Kyu Kim, Hyun‐Yong Yu
Abstract
For the first time, a novel analytical model of contact resistance (<inline-formula> <tex-math notation="LaTeX">${R}_{\text{contact}}$ </tex-math></inline-formula>) in vertically stacked nanosheet FETs (NSHFETs) with a silicide/Si (100) contact for a sub-3-nm node is presented. Generally, <inline-formula> <tex-math notation="LaTeX">${R}_{\text{contact}}$ </tex-math></inline-formula> consists of the interface resistance (<inline-formula> <tex-math notation="LaTeX">${R}_{\text{interface}}$ </tex-math></inline-formula>) and spreading resistance (<inline-formula> <tex-math notation="LaTeX">${R}_{\text{spread}}$ </tex-math></inline-formula>). Herein, a new model of <inline-formula> <tex-math notation="LaTeX">${R}_{\text{interface}}$ </tex-math></inline-formula> of silicide/Si (100) contact, which simultaneously considers the source/drain (S/D) doping concentration (<inline-formula> <tex-math notation="LaTeX">${N}_{\text{si}}$ </tex-math></inline-formula>), Schottky barrier height (SBH), and SBH lowering, is demonstrated simultaneously. In addition, a new model of <inline-formula> <tex-math notation="LaTeX">${R}_{\text{spread}}$ </tex-math></inline-formula> that divides S/D into multiple resistance components for vertically stacked NSHFETs is suggested. In vertically stacked NSHFET with 3-nm node, for TiSi<sub>2</sub>/n-Si (100) and NiPtSi<sub>2</sub>/p-Si (100) contacts, <inline-formula> <tex-math notation="LaTeX">${R}_{\text{spread}}$ </tex-math></inline-formula> shows more than ~50.0% higher values compared to <inline-formula> <tex-math notation="LaTeX">${R}_{\text{interface}}$ </tex-math></inline-formula>. On the other hand, 3-nm node FinFET with TiSi<sub>2</sub>/n-Si (100) and NiPtSi<sub>2</sub>/p-Si (100) contacts, <inline-formula> <tex-math notation="LaTeX">${R}_{\text{spread}}$ </tex-math></inline-formula> shows more than ~53.7% lower values compared to <inline-formula> <tex-math notation="LaTeX">${R}_{\text{contact}}$ </tex-math></inline-formula>. The results show that <inline-formula> <tex-math notation="LaTeX">${R}_{\text{spread}}$ </tex-math></inline-formula> becomes dominant in <inline-formula> <tex-math notation="LaTeX">${R}_{\text{contact}}$ </tex-math></inline-formula> compared to <inline-formula> <tex-math notation="LaTeX">${R}_{\text{interface}}$ </tex-math></inline-formula> when using NSHFETs, in contrast to the conventional FinFETs in which <inline-formula> <tex-math notation="LaTeX">${R}_{\text{interface}}$ </tex-math></inline-formula> is dominant in <inline-formula> <tex-math notation="LaTeX">${R}_{\text{contact}}$ </tex-math></inline-formula>. The high <inline-formula> <tex-math notation="LaTeX">${R}_{\text{spread}}$ </tex-math></inline-formula> 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.