Non-Fourier electrothermal fully coupled analysis of a 5 nm gate-all-around field-effect transistor based on density gradient theory

In the post-Moore era, the three-dimensional fully surrounded channel structure of gate-all-around field-effect transistors (GAAFETs) significantly enhances gate control capabilities. However, its nanoscale features lead to severe overall self-heating effects and thermal spatiotemporal non-uniformity issues. In light of this, we investigated the electrothermal coupling characteristics of a 5 nm GAAFET device numerically. First, a three-dimensional electrothermal coupling simulation framework suitable for nanoscale transistors is established based on the density gradient (DG) model and the phonon hydrodynamic model and solved by the finite element method. Here, the DG model, combined with barrier boundary conditions, is employed to describe the spatial variation of charge carrier density and the quantum confinement effects at the oxide–semiconductor interface. The phonon hydrodynamic equations, along with temperature jump boundary conditions that account for interface phonon scattering, are utilized to characterize the unsteady processes of non-Fourier phonon heat transport. The governing equations for the electric and thermal fields are coupled bidirectionally. The results indicate that the developed electrothermal coupling analysis method under the continuous medium framework takes into account the quantum confinement effects of electrons at the oxide/semiconductor interface, as well as the phonon scattering effects at the interface. It can accurately predict the electrical and thermal processes of GAAFET devices. In contrast, the traditional drift-diffusion model tends to overestimate the predicted current, leading to an overestimation of temperature predictions. This work can be reasonably extended to predict and evaluate the electrothermal performance of other semiconductor devices, thereby providing theoretical support for the reliability design and optimization of novel semiconductor devices.