This work presents a detailed study of the fishbone FET for sub-5 nm technology node, focusing on how three critical geometric parameters like nanosheet width, fin thickness, and oxide thickness, impact both DC and analog/RF performance. By incorporating density gradient quantum correction and appropriate mobility models in Sentaurus TCAD, we accurately capture quantum confinement and scattering effects respectively, within the narrow channels and fins. Increasing the nanosheet width from 25 to 50 nm enhances the on-current by up to 75%. However, a thicker fin (7 nm) significantly increases leakage currents, thereby reducing ION/IOFF and deteriorating subthreshold swing by about 6.5%. In contrast, variations in the SiO₂ interfacial thickness (0.6–0.8 nm) exhibit minimal influence on the DC characteristics. Threshold voltage variations are almost resistant to geometrical effects and can be tuned by varying the gate metal work function. In the RF characteristics, output conductance (gds), intrinsic gain (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">${A}_{{v}_{o}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>A</mi> <msub> <mi>v</mi> <mi>o</mi> </msub> </msub> </math></EquationSource> </InlineEquation>) and the maximum oscillation frequency (fmax) are highly sensitive to parasitic effects, showing a non-monotonic response to both fin thickness and oxide thickness. The transconductance (gm) increases by 75% when increasing the nanosheet width from 25 to 50 nm. But, due to the dominance of gate capacitance, there is a drop in cut-off frequency (fT). However, fT increases by 6% with the increase in SiO2 thickness. The intrinsic gain, transconductance generation factor (TGF), transconductance frequency product (TFP), and intrinsic delay have also been reported. Further, the fishbone FET has been benchmarked against the nanosheet FET, where the fishbone FET showed better performance in ION, gm, fT, and fmax, with a slight degradation in Av0, due to increased gds. These findings show that optimising the nanosheet width, fin dimensions, and oxide parameters is crucial to achieve a balanced performance in DC and analog/RF characteristics.

Impact of Geometrical Variations on DC and Analog/RF Characteristics of Fishbone FET

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发表日期：

2026年2月10日

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Sai Lakshmi Prasanth Kannam,
Kritika Roy,
Rajan Kumar Pandey

摘要

This work presents a detailed study of the fishbone FET for sub-5 nm technology node, focusing on how three critical geometric parameters like nanosheet width, fin thickness, and oxide thickness, impact both DC and analog/RF performance. By incorporating density gradient quantum correction and appropriate mobility models in Sentaurus TCAD, we accurately capture quantum confinement and scattering effects respectively, within the narrow channels and fins. Increasing the nanosheet width from 25 to 50 nm enhances the on-current by up to 75%. However, a thicker fin (7 nm) significantly increases leakage currents, thereby reducing I_ON/I_OFF and deteriorating subthreshold swing by about 6.5%. In contrast, variations in the SiO₂ interfacial thickness (0.6–0.8 nm) exhibit minimal influence on the DC characteristics. Threshold voltage variations are almost resistant to geometrical effects and can be tuned by varying the gate metal work function. In the RF characteristics, output conductance (g_ds), intrinsic gain ( ${A}_{{v}_{o}}$ $A_{v_{o}}$ ) and the maximum oscillation frequency (f_max) are highly sensitive to parasitic effects, showing a non-monotonic response to both fin thickness and oxide thickness. The transconductance (g_m) increases by 75% when increasing the nanosheet width from 25 to 50 nm. But, due to the dominance of gate capacitance, there is a drop in cut-off frequency (f_T). However, f_T increases by 6% with the increase in SiO₂ thickness. The intrinsic gain, transconductance generation factor (TGF), transconductance frequency product (TFP), and intrinsic delay have also been reported. Further, the fishbone FET has been benchmarked against the nanosheet FET, where the fishbone FET showed better performance in I_ON, g_m, f_T, and f_max, with a slight degradation in A_v0, due to increased g_ds. These findings show that optimising the nanosheet width, fin dimensions, and oxide parameters is crucial to achieve a balanced performance in DC and analog/RF characteristics.