Electrothermal Small-Signal Model of Nanosheet FETs With Zero-Temperature-Coefficient Based Parameters Extraction Method

• Published in: IEEE transactions on electron devices Vol. 71; no. 7; pp. 4153 - 4159
• Main Authors: Lyu, Yaoyang, Chen, Wangyong, Cai, Linlin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-07-2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Capacitance; Circuit design; Data models; Equivalent circuits; Field effect transistors; High temperature effects; Integrated circuit modeling; Logic gates; Mathematical models; Modelling; Nanosheet FET (NSFET); Nanosheets; Parameter extraction; Parameters; self-heating effect (SHE); small-signal model; thermal network; Thermal resistance; zero-temperature coefficient (ZTC)
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2024.3395413

Nanosheet FET (NSFET) is a promising structure for scaling transistors to the sub-5-nm node. However, the self-heating effect (SHE) impacts device performance at gigahertz frequencies, necessitating the small-signal modeling that accommodates SHE. Thus, an electrothermal coupled small-signal equivalent circuit model of NSFET and the corresponding parameters extraction method are introduced in this article. The introduced model is verified with TCAD simulated data, achieving excellent agreement between simulated and modeled S -parameters with a modeling error under 1.86%. A zero-temperature coefficient (ZTC)-based thermal network parameter extraction method is proposed, to accurately characterize SHE, enhancing stability of the extracted thermal resistance (<inline-formula> <tex-math notation="LaTeX">{R} _{\text {th}} </tex-math></inline-formula>) and capacitance (<inline-formula> <tex-math notation="LaTeX">{C} _{\text {th}} </tex-math></inline-formula>) at different <inline-formula> <tex-math notation="LaTeX">{V} _{\text {gs}} </tex-math></inline-formula>. The effectiveness of <inline-formula> <tex-math notation="LaTeX">{R} _{\text {th}} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">{C} _{\text {th}} </tex-math></inline-formula> is confirmed by small-signal model parameters extracted from TCAD data, achieving improved accuracy at low frequencies. The bias and temperature rise (<inline-formula> <tex-math notation="LaTeX">\Delta </tex-math></inline-formula> T ) dependencies of intrinsic model parameters and underlying physical mechanisms are discussed. Results reveal that SHE negatively impacts <inline-formula> <tex-math notation="LaTeX">{g} _{m} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">{g} _{\text {ds}} </tex-math></inline-formula>, but positively affects <inline-formula> <tex-math notation="LaTeX">{C} _{\text {ds}} </tex-math></inline-formula>. Moreover, <inline-formula> <tex-math notation="LaTeX">\tau _{m} </tex-math></inline-formula> is positively impacted at <inline-formula> <tex-math notation="LaTeX">{V} _{\text {gs}} </tex-math></inline-formula> below ZTC and negatively affected at <inline-formula> <tex-math notation="LaTeX">{V} _{\text {gs}} </tex-math></inline-formula> above ZTC. This introduced small-signal model provides valuable feedback for NSFET-based RF circuit design under SHE conditions.