Thermal Conductivity Model Of Dielectric Thin Film Based On Near-Field Radiation

The micro thin film material is an important component of the large scale integrated circuits, laser devices, and MEMS. The thin film thermal property affects performance and reliability of the devices and systems. The traditional heat transfer theory, such as Fourier heat conduction law and Planck blackbody radiation law, is not always applicable for the microscale heat transfer problems. A new microscale heat transfer model is described in order to solve the problems. The study of the thin dielectric film thermal property and heat transfer principle has great significance for the device design and operation.According to the low-dimensional dielectric material phonon heat transport mechanism, the dielectric thin film heat transfer mechanism is analyzed. The experiment dates of 3ωmethod measuring the thin film thermal conductivity are analyzed, and SiO₂ is taken as an example to summary the film thermal conductivity measurement tests. The result shows that the thin film thermal conductivity has no clear dependency relationship with the film thickness. It is contrary to the classical theories, which suggests the film surface phonon scattering results in the thin film thermal conductivity decrease with film thickness.A theoretical model is established based on near-field radiation theory and experimental result. The thin films thermal conductivity of SiO₂ is calculated under the theoretical model. The result reveals that the SiO₂ film thermal conductivity decreases with thickness, but the variation is not obvious in the nanometer or micrometer orders. Even when the film thickness is 30nm, the film thermal conductivity is only one ten thousandth less than the thermal conductivity.The Boltzmann Transport Equation (BET) and the local density of states (LDOS) equation is linked to analysis the unity of film thermal conductivity and near-field radiation, and verify whether thermal conductivity of dielectric thin film model is reasonable. The conclusions are consistent with some reported experimental results and theoretical analysis. The film thermal conductivity and near-field radiation is unified in the micro scale. The theoretical model, using near-field radiation to get the film thermal conductivity, is reliable.