Temperature Dependence of Thermal Conductivity for Silicon Dioxide

Heat transport of dielectric thin films in 30–300 nm thick is characterized in the temperature range of 74–300 K using the 3ω method, which is a simple method to measure the cross-plane thermal conductivity of dielectric thin films. Dielectric film samples of two kinds, deposited on Si substrates using plasma enhanced chemical vapor deposition (PECVD) and grown by thermal oxidation, were measured. In order to broaden the application of 3ω method, 3ω method system was combined with cryogenics system to measure temperature dependent material property. SiO₂ films, prepared by thermal oxidation and PECVD, have been put and measured in the cryogenics system. The apparent thermal conductivity, intrinsic thermal conductivity, and interface resistance have been analyzed in different temperature. For this experiment, we discovered the thermal conductivity of PECVD SiO₂ films is smaller than the thermal conductivity of SiO₂ grown by thermal oxidation, because the porosity of thermal SiO₂ is smaller than PECVD SiO₂. The apparent thermal conductivity of SiO₂ film decreases with film thickness. The thickness dependent thermal conductivity is interpreted in terms of a small interface thermal resistance R_I. For SiO₂ films, the thermal conductivity decreases if the temperature decreases, because the mean free path of heater carriers increases.