Simultaneous Evaluation of Heat Capacity and In-plane Thermal Conductivity of Nanocrystalline Diamond Thin Films

ABSTRACT As wide bandgap electronic devices have continued to advance in both size reduction and power handling capabilities, heat dissipation has become a significant concern. To mitigate this, chemical vapor deposited (CVD) diamond has been demonstrated as an effective solution for thermal management of these devices by directly growing onto the transistor substrate. A key aspect of power and radio frequency (RF) electronic devices involves transient switching behavior, which highlights the importance of understanding the temperature dependence of a material’s heat capacity and thermal conductivity when modeling and predicting a devices electro-thermal response. Due to the complicated microstructure near the interface between CVD diamond and electronic material, it is difficult to measure both properties simultaneously. In this work, we use time-domain thermoreflectance (TDTR) to simultaneously measure the in-plane thermal conductivity and heat capacity of a 1-µm-thick CVD diamond film via multi-frequency analysis. We obtain temperature dependent thermal properties by using the pump beam to heat the sample according to increasing power. This mitigates the need for a more complicated setup using a thermal stage but has limited upper temperature boundaries based on the sample geometry and thermal properties. The results show that the in-plane thermal conductivity varied slightly with an average of 103 W/m-K over a temperature range of 302–327 K, while the specific heat capacity has a strong temperature dependence over the same range and compares well with heat capacity data of natural diamond in literature.