Combined thermo-physical investigations of thin layers with Time Domain Thermoreflectance and Scanning Thermal Microscopy on the example of 500 nm thin, CVD grown tungsten

Abstract Time Domain Thermoreflectance (TDTR) and Scanning Thermal Microscopy (SThM) are valuable tools for thermal characterization of thin films. In this work, TDTR–SThM compatibility is demonstrated by quantitative measurements of the thermal conductivity (λ) on a 500 nm thin, CVD grown W-layer. The picosecond laserflash equipment TDTR assesses λ through thermal diffusivity normal to the surface. SThM directly measures λ on the sample surface quantitatively by the 3ω method. TDTR–SThM both show that room temperature λis altered by heat treatment: On the as deposited W-layer, λ is about 153 W/mK. After a short heat treatment (2.5 minutes at 425 °C), λ decreases to about 147 W/mK, while a long heat treatment (4 cycles of ˜20 minutes at 425 °C) increases λ to ˜155 W/mK. This change in λ is attributed to a grain size change, shown by theoretical calculations considering grain boundary scattering.