Measurement of the thermal conductivity of nanometer scale thin films by thermoreflectance phenomenon

We have measured the temperature dependence of thermal conductivity up to several hundred degrees for memory device materials. In the measurement of thermal conductivity, we used a novel technique of nanosecond thermoreflectance measurement spectroscopy (Nano-TheMS) developed by Baba et al. The main advantage of this technique is that it can measure thin films of nanometer-order by easy sample preparation. Using this system with a heat stage, the measurement of thermal conductivities of Ge₂Sb₂Te₅ and ZnS-SiO₂, which were selected as representative materials of memory devices, from room temperature to 400 or 500 °C was carried out. All thermal conductivities increased with higher temperature. Using their temperature dependence, optical disk thermal simulation was carried out, and the results were compared with conventional calculated results without the dependence. It was found that the largest difference at maximum temperature was approximately 80 °C. The temperature dependence of thermal properties is essential for realistic temperature simulation.