Development of three-layer heat diffusion model and high thermal conductivity measurement system
In recent decades, the development of advanced micro and nanoscale size electronics and devices has seen a surge in the various field including semiconductor industry. The feature size of these devices and electronics are already less than 10 nm. Following this development of devices, the power density has increased. Heat dissipation in the devices affect the efficiency, stability, and reliability of the devices. Measurement of thermal conductivity of the materials and understanding of the heat transfer in the materials are required to search for thermal management materials. In this work, the Three-layer heat diffusion model is developed to extract the inplane, cross-plane thermal conductivity and thermal resistance accurately with novel grating imaging techniques expanding previous Two-layer model. The three-layer model is validated by comparing the results with the temperature change curve obtained from the Two-layer model, and Transient thermoreflectance (TTR) multilayer heat diffusion model with the fitting process to extract the heat properties in Au, and glass materials. Also, a new TTR technique based on a ring-shaped pump laser beam with a pair of axicon lenses is developed for measuring high-thermal conductivity materials. The 15 μm and 18 μm ring-shaped pump beam and a 7 μm diameter circular probe beam at the center are formed at the Au and HOPG sample surfaces to measure the thermoreflectance signal. Furthermore, the existence of time delay is confirmed using offset measurement. In a meantime, the instant temperature rise in the ring-shaped pump is observed by measuring high-thermal conductivity materials with axicon lenses.