A 915 MHz/75 kW cylindrical cavity type microwave plasma chemical vapor deposition reactor with a ladder-shaped circumferential antenna developed for growing large area diamond films

Abstract A 915 MHz/75 kW cylindrical cavity type microwave plasma chemical vapor deposition reactor was set up by scaling a 2.45 GHz TM 021 mode microwave resonant cavity. The new reactor retains a cylindrical geometry, which makes it possible to set up an adjustment mechanism for plasma distribution in the reactor during its operation. In addition, a ladder-shaped circumferential antenna was used as the microwave coupling mechanism, so that sealing reliability of the deposition chamber and high power capability of the reactor are ensured. Experimentally, 3–5 inch diameter crack-free diamond films were prepared. The pressure was set at between 15 and 20 kPa and input power used was between 40 and 60 kW, respectively. Growth rate of diamond films ranged between 1.6 and 5.6 μm/h for different size and quality materials, with deviations in thickness within a range of about ± 4% and ± 8% over 3 and 5 inch areas. Morphology, crystalline quality as well as purity of the diamond films were characterized by using optical microscopy, Raman and photoluminescence spectra, and the results proved that the quality and the purity of the diamond films were excellent.