Theoretical And Experimental Research On Non-Equilibrium Thermal Conductivity Of Nanoscale Thin Films

In MEMS and microelectronics devices, metallic and non-metallic thin films are widely used because of the own characteristics of light, heat, sound, mechanical, and electrical. Along with scientific and technological progress as well as the continued miniaturization of electronic devices progress, nano-film thermal transmission has become the current scientific research hot spot. Past studies in the thin heat conduction of film materials were on the basis of balance conditions. Actually, the mean free path of phonon in nano-film structure is larger than the size of films, which are not satisfied with the balance of heat conduction conditions. The heat transfer in nano-film is non-equilibrium. Therefore, it has important significance to study non-equilibrium thermal conductivity of nano film.Because of the low accuracy of theoretical result, the influence factors and the complex solving process, the non-equilibrium theoretical method is not suitable. Therefore experimental method is used to measure the thermal conductivity of nano-thin film measurement in this paper. By comparing four popular measurement methods for thermal conductivity of films, it is found that 3ωmethod is a transient electric heating method, and measurement is a moment to complete, not a lasting steady process, therefore 3ωmethod can be used to measure nano-film non-equilibrium thermal conductivity. To ensure the quality of experimental samples, SiO2 thin film and Si3 N 4 thin film is prepared by PECVD. Firstly the thermal conductivity of SiO2 thin films is measured to detect the experiment rig. Then the thermal conductivity of Si3 N 4 thin film is measured under different frequencies, different temperature and different heating film heater size. Lastly the best micro-heater size and the suitable frequency for the thermal conductivity are determined.Theoretical and experimental results show that the thermal conductivity of films is extremely non-equilibrium, and the non-equilibrium thermal conductivity of thin film contracts with the phonon mean free path. The thermal conductivity of Si3 N 4film increases with temperature increasing, the experimental result is best under the micro-heater size of 20μmand 24μm.The microstructure and the quality of the samples and the micro-heater have influence the experiment results.