Thermal Conductivity of Diamond Thin-films on Silicon Wafers

Abstract

Synthetic diamond films may play an important role in thermal management of processors. Diamond may be up to four times as thermally conductive as copper, but the conductivity of individual films may vary based on synthesis parameters. Therefore a straightforward nondestructive method is desired to determine thermal characteristics of diamond-coated silicon wafers. Diamond-coated samples were grown via Microwave-Plasma Chemical Vapor Deposition, and characterized for film thickness by pre- and post-deposition weighing and film quality by Raman spectroscopy. The thermal conductivity of samples is measured by three different methods: thermocouples, infrared camera, and Raman spectroscopy. Each measurement setup is based on Fourier�s first law of heat conduction, in which the temperature gradient across a region of material is proportional to the thermal conductivity of the material. Thermocouples were used initially, which allowed for quick feedback on temperature gradients. However, the measurement accuracy was greatly affected by the thermocouple mounting, thus non-contact methods of measurement were considered. Infrared cameras were used to view the temperature profile of the entire system, but it was determined that the surface temperatures visible to the camera were different than the internal temperatures of the experimental setup. Finally, Raman spectroscopy is used to measure temperature and thermal gradient, due to the temperature dependence of the Raman peaks. It was found that the diamond peak of four different films exhibited a thermal shift comparable to published data. This method will be pursued in future research to measure thermal properties of diamond films, including the interfacial thermal characteristics.