Full 3-D Monte Carlo Simulation of Coupled Electron-Phonon Transport: Self-Heating in a Nanoscale FinFET

Abstract

To study coupled electro-thermal transport processes in nanoscale electronic devices, continuum models are no longer sufficient. In this work, we present an effort to couple a three-dimensional (3-D) Monte Carlo Phonon Transport (MCPT) kernel with a 3-D Monte Carlo Electron Transport (MCET) simulator. The phonon-phonon scattering is modeled in relaxation time approximation (RTA) using Holland's formalism. Diffusive boundary collisions for phonons is modeled using the Beckmann-Kirchhoff (B-K) surface roughness scattering formalism considering the effects of phonon wavelength, incident angles and degree of surface roughness. In the electron-phonon coupled platform, acoustic and intervalley g and f type electron-phonon scattering mechanisms are considered and the resulting local temperature modification has been used to bridge the electron and phonon transport paths. The simulator has been validated by modeling the self-heating effect in a nanoscale FinFET device. Here, phonon transport at the oxide-silicon interface has been treated using the Diffuse Mismatch (DM) model, whereas, the phonons in the oxide have been described using the Debye model and temperature and frequency dependent relaxation time. For a FinFET with a gate length of 18 nm, channel width of 4 nm, and a fin height of 8 nm, simulation results show an ON current degradation of as high as ∼7% due to self-heating. The temperature rise in the channel region is found to be ∼30 K.