CVD Diamond Coating of AlN Ceramic Substrates to Enhance Heat Removal

摘要

Polycrystalline diamond coatings over 100 μm thick are produced on AlN ceramic substrates by microwave-plasma CVD from a CH{sub}4-H{sub}2-O{sub}2 mixture. Their Raman spectra indicate good phase purity and a compressive stress as high as about 4 GPa due to the thermal-expansion mismatch between the diamond and the ceramic. Measurements by the laser flash technique at room temperature show the coatings to have a thermal conductivity of 970 W m{sup}(-1)K{sup}(-1) as against 290 and 170 W m{sup}(-1) K{sup}(-1) for mono- and poly crystalline aluminum nitride, respectively. It is concluded that a diamond coating of appropriate thickness significantly enhances the thermal conductivity of the surface region of AlN substrates and therefore could be useful for creating more efficient AlN heat sinks.