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.

Automated summary

We developed a new method of producing composite substrates by growing diamond films on a 4H-SiC substrate to enhance thermal management in GaN-based RF power devices. The morphology, grain orientation, and structure of the diamond films were characterized, and they exhibited uniform and compact properties without voids, gaps, graphite phase, or impurity peak. The thermal conductivity of the composite substrates was simulated and calculated, showing a significant increase compared to pure SiC substrate, and the coefficient of thermal expansion could be engineered by changing the SiC thickness.