This work investigates the effect of TiN metal gate work function variability (WFV) on the electrical parameters of nanosheet field-effect transistors (NSFETs) using the 3D Sentaurus TCAD simulator. The effects of WFV on the threshold voltage (σVT), ON-state current (σION), OFF-state current (σIOFF), and switching ratio σ(ION/IOFF) are highlighted for different gate lengths (Lg), effective widths (Weff), and grain sizes (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\overline{\Phi }$</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mi mathvariant="normal">Φ</mi> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation>). As the gate dimensions shrink into the deep-nanoscale, metal-gate granularity (MGG) produces fluctuations in the effective gate work function, which increases the variation in σVT, σION, σIOFF, and σ(ION/IOFF). As <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\overline{\Phi }$</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mi mathvariant="normal">Φ</mi> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> increases, the fluctuations in electrical parameters increase for different NSFET device dimensions. The results reveal that when <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\overline{\Phi }$</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mi mathvariant="normal">Φ</mi> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> is comparable to device dimensions, the variability of electrical parameters becomes saturated. In addition, the transfer curves for 200 simulated devices and nominal values are plotted at different grain sizes. The results reveal that there are significant variations in drain current as <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\overline{\Phi }$</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mi mathvariant="normal">Φ</mi> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> is increased from 2 nm to 15 nm, and σVT is reduced as the number of stacks increases from two to three. Moreover, the variability in electrical parameters is reported for a p-type NSFET, which shows greater degradation than an n-type NSFET. The variability analysis is highlighted for a wide variation in temperatures, and a comparison of the variation in electrical parameters due to the metal gate is compared with values reported in the literature.

Statistical Work Function Variability of Metal Gate on Electrical Parameters for Nanosheet FET

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发表日期：

2026年7月14日

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Ritik Ranjan,
Saurav Chanda,
Rajesh Saha

摘要

This work investigates the effect of TiN metal gate work function variability (WFV) on the electrical parameters of nanosheet field-effect transistors (NSFETs) using the 3D Sentaurus TCAD simulator. The effects of WFV on the threshold voltage (σV_T), ON-state current (σI_ON), OFF-state current (σI_OFF), and switching ratio σ(I_ON/I_OFF) are highlighted for different gate lengths (L_g), effective widths (W_eff), and grain sizes ( $\overline{\Phi }$ $\bar{Φ}$ ). As the gate dimensions shrink into the deep-nanoscale, metal-gate granularity (MGG) produces fluctuations in the effective gate work function, which increases the variation in σV_T, σI_ON, σI_OFF, and σ(I_ON/I_OFF). As $\overline{\Phi }$ $\bar{Φ}$ increases, the fluctuations in electrical parameters increase for different NSFET device dimensions. The results reveal that when $\overline{\Phi }$ $\bar{Φ}$ is comparable to device dimensions, the variability of electrical parameters becomes saturated. In addition, the transfer curves for 200 simulated devices and nominal values are plotted at different grain sizes. The results reveal that there are significant variations in drain current as $\overline{\Phi }$ $\bar{Φ}$ is increased from 2 nm to 15 nm, and σV_T is reduced as the number of stacks increases from two to three. Moreover, the variability in electrical parameters is reported for a p-type NSFET, which shows greater degradation than an n-type NSFET. The variability analysis is highlighted for a wide variation in temperatures, and a comparison of the variation in electrical parameters due to the metal gate is compared with values reported in the literature.