Heat transport in thin dielectric films

TLDR

The study uses the 3ω method to measure heat transport in 20–300 nm SiO₂ and SiₓNᵧ films deposited on Si by PECVD, interpreting thickness‑dependent conductivity variations as arising from a small interface thermal resistance. PECVD SiO₂ films exhibit thermal conductivities only ~10 % lower than thermally oxidized SiO₂ for thicknesses >100 nm, while PECVD SiₓNᵧ films have about half the conductivity of high‑temperature CVD SiₓNᵧ; for films <50 nm both materials show reduced apparent conductivity, with an interface resistance of ~2×10⁻⁸ K m² W⁻¹ equivalent to a 20 nm SiO₂ layer at room temperature.

Abstract

Heat transport in 20–300 nm thick dielectric films is characterized in the temperature range of 78–400 K using the 3ω method. SiO2 and SiNx films are deposited on Si substrates at 300 °C using plasma enhanced chemical vapor deposition (PECVD). For films &amp;gt;100 nm thick, the thermal conductivity shows little dependence on film thickness: the thermal conductivity of PECVD SiO2 films is only ∼10% smaller than the conductivity of SiO2 grown by thermal oxidation. The thermal conductivity of PECVD SiNx films is approximately a factor of 2 smaller than SiNx deposited by atmospheric pressure CVD at 900 °C. For films &amp;lt;50 nm thick, the apparent thermal conductivity of both SiO2 and SiNx films decreases with film thickness. The thickness dependent thermal conductivity is interpreted in terms of a small interface thermal resistance RI. At room temperature, RI∼2×10−8 K m2 W−1 and is equivalent to the thermal resistance of a ∼20 nm thick layer of SiO2 .