Effects of heating strategies and ballistic transport on the thermal conduction in fin field-effect transistors

Abstract

Efficiently predicting three-dimensional temperature distributions and understanding the non-Fourier thermal conduction mechanism are of great significance for alleviating hotspot issue in fin field-effect transistors (FinFETs). Numerical solutions of the effective Fourier’s law (EFL) and the phonon Boltzmann transport equation (BTE) are two mainstream thermal engineering simulation methods in FinFETs, but continuous heating and steady-state temperature distributions are mainly considered in the previous work. Until today, effects of discontinuous heating on micro/nano scale thermal conduction is rarely studied, and the deviations between the predictions of the EFL and the phonon BTE in FinFETs are rarely compared, either. To answer these questions, three different heating strategies are considered including ‘Continuous’, ‘Intermittent’ and ‘Alternating’ heating, and the heat conduction processes in FinFETs are simulated by both the phonon BTE and EFL. Numerical results show that different heating strategies have great influence on the peak temperature rise and transient thermal dissipation process. Compared to ‘Intermittent’ or ‘Continuous’ heating, the temperature variance of ‘Alternating’ heating is smaller. The peak temperature rise of ‘Alternating’ heating is $28\text{\%}-43.5\text{\%}$ lower than that of ‘Continuous’ heating in FinFETs. The silicon dioxide insulation layer reduces the thermal shock on the bottom substrate material although it raised the overall temperature in the fin area. It is not easy to accurately capture the heat conduction in FinFETs by the EFL, especially near the nanoscale hotspot and corner areas where ballistic phonon transport dominates and the temperature diffusion is no longer valid.