Interfacial microstructure and thermal properties of diamond thin films prepared on Si and SiC substrates by chemical vapor deposition

Abstract

The thermal conductivity ($k$) of thin films is becoming increasingly important in electronic devices because the capability to transport heat is emerging as an essential factor limiting device performance. To assess the impact of film structure, specifically the diamond/Si and SiC/Si interfaces, on thermal transport, this study explores and discusses the microstructure and thermal properties of polycrystalline diamond films. Additionally, the thermal property of the epitaxial growth of 3C-SiC thin film on the corresponding single crystal Si substrate was measured. We utilized time-domain thermoreflectance to measure the $k$ values of diamond films, which ranged from 21 to 276 W/(mK) with thicknesses from 0.63 to 8.7 µm. It was found that grain size and amorphous carbon content in films play a vital role in determining the thermal properties of diamond films. The interfacial thermal conductance of the diamond/Si interface (18 MW/(m²K)) is significantly lower than that of the 3C-SiC/Si interface (78 MW/(m²K)). This reduction is primarily due to the presence of a substantial amorphous layer, a significant mismatch in Debye temperatures, and a lattice constant mismatch between diamond and silicon. Compared to the simulated $k$ of the 3C-SiC, the reduction of $k$ in the 3C-SiC film is primarily due to the presence of numerous stacking faults in the film. This research takes a significant step towards achieving highly thermally conductive material systems, a crucial development for diamond materials and structures across diverse applications.