Thermal Conductivity Measurements of Ultra-Thin Single Crystal Silicon Layers

TLDR

Thermal conduction in ultra‑thin silicon layers critically affects self‑heating of deep submicron transistors and the thermal performance of nanoscale devices. The study measured lateral thermal conductivity of 20‑ and 100‑nm single‑crystal silicon layers between 30 and 450 K using joule heating and electrical‑resistance thermometry on suspended microstructures. Phonon‑boundary scattering dramatically reduces conductivity, with the 20‑nm layer exhibiting ~22 W m⁻¹ K⁻¹ at room temperature versus 148 W m⁻¹ K⁻¹ bulk, and the results agree with Boltzmann‑transport‑equation predictions.

Abstract

Self-heating in deep submicron transistors (e.g., silicon-on-insulator and strained-Si) and thermal engineering of many nanoscale devices such as nanocalorimeters and high-density thermomechanical data storage are strongly influenced by thermal conduction in ultra-thin silicon layers. The lateral thermal conductivity of single-crystal silicon layers of thicknesses 20 and 100nm at temperatures between 30 and 450K are measured using joule heating and electrical-resistance thermometry in suspended microfabricated structures. In general, a large reduction in thermal conductivity resulting from phonon-boundary scattering is observed. Thermal conductivity of the 20nm thick silicon layer at room temperature is nearly 22Wm−1K−1, compared to the bulk value, 148Wm−1K−1. The predictions of the classical thermal conductivity theory that accounts for the reduced phonon mean free paths based on a solution of the Boltzmann transport equation along a layer agrees well with the experimental results.