Growth of 2-inch diamond films on 4H-SiC substrate by microwave plasma CVD for enhanced thermal performance

We report a novel method of producing composite substrates by growing diamond films on a 4H-SiC substrate by microwave plasma chemical vapor deposition to enhance the thermal management for thermal diffusion ap-plications in GaN-based RF power devices. Morphology, grain orientation and structure of the diamond films were characterized by scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and Raman spectroscopy. The diamond films were uniform and compact, without voids and gaps observed via cross-sectional view of microscopy, and without any graphite phase and impurity peak. Thermal conductivity (TC) of the diamond-SiC composite substrates was simulated and calculated. Results indicate that the TC of the com-posite substrates is up to 512.02 +/- 6.37 W m- 1 K-1 when the SiC thickness is 500 mu m, which is 1.53 +/- 0.02 times of the pure SiC substrate, and this high TC increases to 1171.13 +/- 67.23 W m- 1 K-1 after the 4H-SiC substrate is thinned down to 50 mu m. The coefficient of thermal expansion (CTE) of the composite substrates can be engi-neered by changing the thickness of SiC substrate.