Multiscale Thermal Simulation for GAAFET With First-Principles-Based Boltzmann Transport Equation

For next-generation advanced logic devices, gate-all-around field-effect transistors (GAAFETs) with characteristic size reaching the 10 nm scale, necessitate thorough consideration of nanoscale thermal transport to assess the impact of self-heating on device performance and reliability. However, previous studies predominantly relied on simplified or fitting models to directly adjust the effective thermal conductivities of various device components within the heat diffusion equation (HDE) or thermal resistance networks. These methods are inadequate for fully capturing nanoscale thermal transport. Here, we perform multiscale thermal simulations of GAAFETs by integrating first-principles-based nongray Boltzmann transport equation (BTE) with the HDE. By comparing the temperature distributions calculated using the gray BTE and HDE, we demonstrate the necessity of employing the nongray phonon BTE for accurate simulation of the active region. We further discover that the size-dependent thermal conductivity of metal regions should be incorporated using the electron–phonon BTE. Moreover, based on comprehensive thermal simulations of a stacked nanosheet GAAFET, we identify that the amorphous passive layer, interfacial thermal resistance between different layers, along with the thermal resistance of the STI/BDI layers and interconnections, are key factors limiting heat dissipation. Our approach fully incorporates nanoscale thermal transport while eliminating reliance on empirical parameters and facilitates multiscale simulations from materials to structures to devices, with potential applicability to circuit-level simulations.