The 8-inch free-standing CVD diamond wafer fabricated by DC-PACVD

We report the fabrication of the 8-inch free-standing CVD diamond wafers by DC-PACVD process with the diode-type electrode configuration. Methane-hydrogen gas mixture was used as the precursor gas. The methane volume % in hydrogen, the gas flow rate and the chamber pressure were 5 similar to 12%, 400 sccm and 100 similar to 130 Torr, respectively. The discharge voltage and the discharge current were 840 910 V and 90 similar to 110 A. respectively. The substrate temperature was 1200 similar to 1300 degrees C. The thermal conductivity, crystallinity and microstructure were characterized by the converging thermal wave technique. Raman spectroscopy, optical microscopy and SEM, respectively. The maximum growth rate was 9 mu m/h for thermal grade 8-inch wafer. The deviation of thickness and the thermal conductivity over the 8-inch wafer was around 10% of the respective averaged values. The distribution of FWHM of Raman diamond peak over the wafer surface also showed excellent uniformity. The extremely simple scale-up of the present deposition technology was demonstrated. (c) 2010 Elsevier B.V. All rights reserved.