A circumferential antenna ellipsoidal cavity type MPCVD reactor developed for diamond film deposition

Abstract

In this paper, a new circumferential antenna ellipsoidal cavity type MPCVD reactor possessing advantages of both an ellipsoidal cavity type and a multimode non-cylindrical cavity type MPCVD reactor is described. An ellipsoidal cavity is adopted as its deposition chamber and a circumferential antenna is used in its microwave coupling channel. A ring-shaped quartz window located within the microwave coupling channel has replaced the quartz bell jar that has been used by a conventional ellipsoidal cavity type MPCVD reactor. Therefore, input microwave power of the reactor will be no longer constrained by the quartz bell jar. At the same time, sealing reliability of the microwave window is improved. Using the new reactor, a 2-inch diameter freestanding diamond film has been synthesized at 6kW input power, and Raman spectroscopy analyses indicate that the diamond film prepared using the new reactor is of high quality.Resonant electric field patterns of different sized ellipsoidal cavities were systematically simulated and analyzed. Based on the simulation, a novel circumferential antenna ellipsoid cavity type MPCVD reactor was built. The new MPCVD reactor combines the advantages of an ellipsoidal cavity and a circumferential antenna. Also a ring-shaped quartz window is adopted to replace a conventionally used quartz bell jar as its microwave feeding window. Such a design makes the reactor get rid of the limitation in microwave power levels resulting from usage of the bell jar. Two-inch high quality diamond films have been deposited using the newly built reactor at high input microwave power.