Session: 04-04: Nano/Microscale Boiling and Condensation Heat Transfer

Paper Number: 131554

131554 - First-Principles Based Non-Fourier Thermal Analysis for Nanoscale Devices 

Abstract: 

Thermal analysis is an essential component of device simulation for device design and thermal management. The prevalent approach of device thermal analysis employs Fourier-law-based heat diffusion equation. However, Fourier’s law is known to fail at small scales when the characteristic length is smaller than the phonon mean free path and non-Fourier effects should be taken into consideration. To date, achieving accurate and efficient non-Fourier thermal analysis for three-dimensional (3D) small-scale devices remains a challenge.

In this study, we implement non-Fourier thermal analysis of devices by utilizing the first-principles based nongray Boltzmann Transport Equation (BTE). Non-Fourier effects are considered in both thermal generation and transport processes. In the thermal generation process, electrons gain energy under the electric field and transfer the energy to phonons. Since there is a wide range of phonon properties due to phonon dispersion and polarization, the total energy is allocated among different phonon modes and the non-Fourier effects originate from the electron’s preference to transfer energy to specific phonon modes. In the thermal transport process, phonons with mean free path (MFP) comparable to or larger than the size of device no longer transport diffusively and the non-Fourier effects lie in the ballistic phonon transport.

A three-dimensional structure of silicon-based fin field effect transistors (FinFET) is adopted as a case study. We use first-principles method to investigate the selective electron-phonon energy transfer process, and obtain the mode-level phonon generation rates. Then, we solve the nongray phonon BTE to determine the temperature distribution of the devices, by an efficient phonon BTE solver developed by our research group, GiftBTE. Through comparisons with heat diffusion equation and previous models, we demonstrate the considerable impact of non-Fourier effects on device temperature rise. Furthermore, we experimentally measure the average gate temperature of the device, which is in close agreement with our first-principles BTE predictions. In contrast, classical heat diffusion equations significantly underestimate the temperature rise, demonstrating the necessity of incorporating phonon BTE into device thermal analysis.

Our approach has several highlights: (1) All input parameters, including phonon properties and heat sources based on electron-phonon interactions, are obtained from first-principles calculations, eliminating the need for empirical fitting parameters. (2) Through the implementation of an efficient numerical solver, we have enabled the calculation of the phonon BTE for realistic 3D device thermal analysis within an hour on a personal laptop. (3) Our approach shows a thermal analysis with a high accuracy in comparison with experimental results, and it can be readily extended to a variety of devices and operating conditions. (4) This approach emphasizes the pivotal role of material properties in device modeling and provides a potential multiscale design framework that bridges the gap between materials, devices, and applications.

Presenting Author: Yufei Sheng Shanghai Jiao Tong University

Presenting Author Biography: Yufei Sheng, a doctoral candidate at Shanghai Jiao Tong University, is currently engaged in research focused on the self-heating mechanisms of nanodevices, as well as the development of electro-thermal device simulation method.

Authors:

Yufei Sheng Shanghai Jiao Tong University
Hua Bao Shanghai Jiao Tong University