Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

Abstract In this work, we report on the measurement of the thermal conductivity of thin insulating films of SiO 2 obtained by thermal oxidation, and Al 2 O 3 grown by atomic layer deposition (ALD), both on Si wafers. We used photoreflectance microscopy to determine the thermal properties of the films as a function of thickness in the 2 nm to 1000 nm range. The effective thermal conductivity of the Al 2 O 3 layer is shown to decrease with thickness down to 70% for the thinnest layers. The data were analyzed upon considering that the change in the effective thermal conductivity corresponds to an intrinsic thermal conductivity associated to an additional interfacial thermal resistance. The intrinsic conductivity and interfacial thermal resistance of SiO 2 were found to be equal to 0.95 W/m·K and 5.1 × 10 − 9  m 2 K/W respectively; those of Al 2 O 3 were found to be 1.56 W/m·K and 4.3 × 10 − 9  m 2 K/W.